diff --git a/src/win32/fb_d3d9.cpp b/src/win32/fb_d3d9.cpp
index 08f2e2ed4..ff1c0d9c6 100644
--- a/src/win32/fb_d3d9.cpp
+++ b/src/win32/fb_d3d9.cpp
@@ -3293,8 +3293,8 @@ void D3DFB::FillSimplePoly(FTexture *texture, FVector2 *points, int npoints,
 				quad->Flags |= BQF_Desaturated;
 			}
 			quad->ShaderNum = BQS_InGameColormap;
-			color0 = D3DCOLOR_ARGB(colormap->Desaturate,
-				colormap->Color.r, colormap->Color.g, colormap->Color.b);
+			quad->Desat = colormap->Desaturate;
+			color0 = D3DCOLOR_ARGB(255, colormap->Color.r, colormap->Color.g, colormap->Color.b);
 			double fadelevel = clamp(shade / (NUMCOLORMAPS * 65536.0), 0.0, 1.0);
 			color1 = D3DCOLOR_ARGB(DWORD((1 - fadelevel) * 255),
 				DWORD(colormap->Fade.r * fadelevel),
@@ -3532,6 +3532,10 @@ void D3DFB::EndQuadBatch()
 			{
 				break;
 			}
+			if (quad->ShaderNum == BQS_InGameColormap && (quad->Flags & BQF_Desaturated) && quad->Desat != q2->Desat)
+			{
+				break;
+			}
 			indexpos += q2->NumTris * 3;
 			vertpos += q2->NumVerts;
 		}
@@ -3593,6 +3597,10 @@ void D3DFB::EndQuadBatch()
 			select = !!(quad->Flags & BQF_Desaturated);
 			select |= !!(quad->Flags & BQF_InvertSource) << 1;
 			select |= !!(quad->Flags & BQF_Paletted) << 2;
+			if (quad->Flags & BQF_Desaturated)
+			{
+				SetConstant(PSCONST_Desaturation, quad->Desat / 255.f, (255 - quad->Desat) / 255.f, 0, 0);
+			}
 			SetPixelShader(Shaders[SHADER_InGameColormap + select]);
 		}
 
@@ -3704,6 +3712,7 @@ bool D3DFB::SetStyle(D3DTex *tex, DrawParms &parms, D3DCOLOR &color0, D3DCOLOR &
 	stencilling = false;
 	quad.Palette = NULL;
 	quad.Flags = 0;
+	quad.Desat = 0;
 
 	switch (style.BlendOp)
 	{
@@ -3812,7 +3821,8 @@ bool D3DFB::SetStyle(D3DTex *tex, DrawParms &parms, D3DCOLOR &color0, D3DCOLOR &
 				quad.Flags |= BQF_Desaturated;
 			}
 			quad.ShaderNum = BQS_InGameColormap;
-			color0 = D3DCOLOR_ARGB(parms.colormapstyle->Desaturate,
+			quad.Desat = parms.colormapstyle->Desaturate;
+			color0 = D3DCOLOR_ARGB(color1 >> 24,
 				parms.colormapstyle->Color.r,
 				parms.colormapstyle->Color.g,
 				parms.colormapstyle->Color.b);
diff --git a/src/win32/win32iface.h b/src/win32/win32iface.h
index fc75af0a3..5314fc667 100644
--- a/src/win32/win32iface.h
+++ b/src/win32/win32iface.h
@@ -296,6 +296,7 @@ private:
 			};
 			DWORD Group1;
 		};
+		BYTE Desat;
 		D3DPal *Palette;
 		IDirect3DTexture9 *Texture;
 		WORD NumVerts;		// Number of _unique_ vertices used by this set.
@@ -304,6 +305,7 @@ private:
 
 	enum
 	{
+		PSCONST_Desaturation = 1,
 		PSCONST_PaletteMod = 2,
 		PSCONST_Weights = 6,
 		PSCONST_Gamma = 7,
diff --git a/wadsrc/static/shaders/d3d/shaders.ps b/wadsrc/static/shaders/d3d/shaders.ps
index a650cd84a..827b52855 100644
--- a/wadsrc/static/shaders/d3d/shaders.ps
+++ b/wadsrc/static/shaders/d3d/shaders.ps
@@ -6,6 +6,7 @@ sampler1D Gamma2 : register(s3);
 sampler1D Gamma3 : register(s4);
 #endif
 
+float4 Desaturation : register(c1);	// { Desat, 1 - Desat }
 float4 PaletteMod : register(c2);
 float4 Weights : register(c6);		// RGB->Gray weighting { 77/256.0, 143/256.0, 37/256.0, 1 }
 float4 Gamma : register(c7);
@@ -70,15 +71,16 @@ float4 SpecialColormap(float2 tex_coord : TEXCOORD0, float4 start : COLOR0, floa
 	float4 range = end - start;
 	// We can't store values greater than 1.0 in a color register, so we multiply
 	// the final result by 2 and expect the caller to divide the start and end by 2.
-	color.rgb = 2 * (start + Grayscale(color) * range);
+	color.rgb = 2 * (start + Grayscale(color) * range).rgb;
 	// Duplicate alpha semantics of NormalColor.
 	color.a = start.a + color.a * end.a;
 	return color;
 }
 
 // In-game colormap effect: fade to a particular color and multiply by another, with 
-// optional desaturation of the original color. Desaturation is packed into color.a.
+// optional desaturation of the original color. Desaturation is stored in c1.
 // Fade level is packed int fade.a. Fade.rgb has been premultiplied by alpha.
+// Overall alpha is in color.a.
 float4 InGameColormap(float2 tex_coord : TEXCOORD0, float4 color : COLOR0, float4 fade : COLOR1) : COLOR
 {
 	float4 rgb = SampleTexture(tex_coord);
@@ -86,17 +88,16 @@ float4 InGameColormap(float2 tex_coord : TEXCOORD0, float4 color : COLOR0, float
 	// Desaturate
 #if DESAT
 	float3 intensity;
-	float invdesat;
-	intensity.rgb = Grayscale(rgb) * color.a;
-	invdesat = Weights.w - color.a;
-	rgb.rgb = intensity + rgb * invdesat;
+	intensity.rgb = Grayscale(rgb) * Desaturation.x;
+	rgb.rgb = intensity.rgb + rgb.rgb * Desaturation.y;
 #endif
 
 	// Fade
 	rgb.rgb = rgb.rgb * fade.aaa + fade.rgb;
 
-	// Shade
-	rgb.rgb = rgb.rgb * color.rgb;
+	// Shade and Alpha
+	rgb = rgb * color;
+
 	return rgb;
 }
 
diff --git a/wadsrc/static/shaders/d3d/sm14/InGameColormap.pso b/wadsrc/static/shaders/d3d/sm14/InGameColormap.pso
index e1a99904b..18a747196 100644
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diff --git a/wadsrc/static/shaders/d3d/sm14/InGameColormapDesat.pso b/wadsrc/static/shaders/d3d/sm14/InGameColormapDesat.pso
index 2bafecca0..9eedbdadc 100644
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diff --git a/wadsrc/static/shaders/d3d/sm14/InGameColormapInv.pso b/wadsrc/static/shaders/d3d/sm14/InGameColormapInv.pso
index 0cf0808b0..4122e261a 100644
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diff --git a/wadsrc/static/shaders/d3d/sm14/InGameColormapInvDesat.pso b/wadsrc/static/shaders/d3d/sm14/InGameColormapInvDesat.pso
index 286c765e2..4b2b2268a 100644
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diff --git a/wadsrc/static/shaders/d3d/sm14/InGameColormapPal.pso b/wadsrc/static/shaders/d3d/sm14/InGameColormapPal.pso
index f6a6a6fba..d8294f663 100644
Binary files a/wadsrc/static/shaders/d3d/sm14/InGameColormapPal.pso and b/wadsrc/static/shaders/d3d/sm14/InGameColormapPal.pso differ
diff --git a/wadsrc/static/shaders/d3d/sm14/InGameColormapPalDesat.pso b/wadsrc/static/shaders/d3d/sm14/InGameColormapPalDesat.pso
index 57892bae1..daec85c3a 100644
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diff --git a/wadsrc/static/shaders/d3d/sm14/InGameColormapPalInv.pso b/wadsrc/static/shaders/d3d/sm14/InGameColormapPalInv.pso
index 3964f59dc..e94efa48a 100644
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diff --git a/wadsrc/static/shaders/d3d/sm14/InGameColormapPalInvDesat.pso b/wadsrc/static/shaders/d3d/sm14/InGameColormapPalInvDesat.pso
index 7a3850318..c75fd148d 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/BurnWipe.pso b/wadsrc/static/shaders/d3d/sm20/BurnWipe.pso
index dba002169..b1daa59be 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/GammaCorrection.pso b/wadsrc/static/shaders/d3d/sm20/GammaCorrection.pso
index 10112243d..92251eb02 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/InGameColormap.pso b/wadsrc/static/shaders/d3d/sm20/InGameColormap.pso
index 29a67c1ec..7ef9f5322 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/InGameColormapDesat.pso b/wadsrc/static/shaders/d3d/sm20/InGameColormapDesat.pso
index 78ba2c4ac..2a87e6e96 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/InGameColormapInv.pso b/wadsrc/static/shaders/d3d/sm20/InGameColormapInv.pso
index be962db51..98ff0cc38 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/InGameColormapInvDesat.pso b/wadsrc/static/shaders/d3d/sm20/InGameColormapInvDesat.pso
index 8387b5b80..3605fb6ba 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/InGameColormapPal.pso b/wadsrc/static/shaders/d3d/sm20/InGameColormapPal.pso
index 0eed147cd..bccbbc004 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/InGameColormapPalDesat.pso b/wadsrc/static/shaders/d3d/sm20/InGameColormapPalDesat.pso
index 8029e484e..3f08538b1 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/InGameColormapPalInv.pso b/wadsrc/static/shaders/d3d/sm20/InGameColormapPalInv.pso
index acdd60934..14c602bc4 100644
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index f9adfebdf..ac3e5dc67 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/NormalColor.pso b/wadsrc/static/shaders/d3d/sm20/NormalColor.pso
index a132b7082..530002972 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/NormalColorInv.pso b/wadsrc/static/shaders/d3d/sm20/NormalColorInv.pso
index e18767e87..da470159a 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/NormalColorPal.pso b/wadsrc/static/shaders/d3d/sm20/NormalColorPal.pso
index 68a1f3fac..57b34eb35 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/NormalColorPalInv.pso b/wadsrc/static/shaders/d3d/sm20/NormalColorPalInv.pso
index 8276561f0..2c490574c 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/RedToAlpha.pso b/wadsrc/static/shaders/d3d/sm20/RedToAlpha.pso
index cd74d5586..10fa58af8 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/RedToAlphaInv.pso b/wadsrc/static/shaders/d3d/sm20/RedToAlphaInv.pso
index 1aeadb9fb..792ffbf35 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/SpecialColormap.pso b/wadsrc/static/shaders/d3d/sm20/SpecialColormap.pso
index 4258efed5..24ebb375a 100644
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index d8c347c63..b706962aa 100644
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diff --git a/wadsrc/static/shaders/d3d/sm20/VertexColor.pso b/wadsrc/static/shaders/d3d/sm20/VertexColor.pso
index 7f899a57b..bd62a1d29 100644
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diff --git a/wadsrc/static/shaders/d3d/sm30/BurnWipe.pso b/wadsrc/static/shaders/d3d/sm30/BurnWipe.pso
index 0626821f7..50e942ab3 100644
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diff --git a/wadsrc/static/shaders/d3d/sm30/GammaCorrection.pso b/wadsrc/static/shaders/d3d/sm30/GammaCorrection.pso
index f1a4dba10..662f59f37 100644
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diff --git a/wadsrc/static/shaders/d3d/sm30/InGameColormap.pso b/wadsrc/static/shaders/d3d/sm30/InGameColormap.pso
index 4f0bb474c..82f702f84 100644
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diff --git a/wadsrc/static/shaders/d3d/sm30/InGameColormapDesat.pso b/wadsrc/static/shaders/d3d/sm30/InGameColormapDesat.pso
index 593d69f5b..44d67d57b 100644
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diff --git a/wadsrc/static/shaders/d3d/sm30/InGameColormapInv.pso b/wadsrc/static/shaders/d3d/sm30/InGameColormapInv.pso
index 35fba3f93..78d4abc9d 100644
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diff --git a/wadsrc/static/shaders/d3d/sm30/InGameColormapInvDesat.pso b/wadsrc/static/shaders/d3d/sm30/InGameColormapInvDesat.pso
index 2dc07bb0a..2da2e7b20 100644
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diff --git a/wadsrc/static/shaders/d3d/sm30/InGameColormapPal.pso b/wadsrc/static/shaders/d3d/sm30/InGameColormapPal.pso
index 8facb7f12..8de88be2a 100644
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diff --git a/wadsrc/static/shaders/d3d/sm30/InGameColormapPalDesat.pso b/wadsrc/static/shaders/d3d/sm30/InGameColormapPalDesat.pso
index 8a887b064..ad57fb576 100644
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diff --git a/wadsrc/static/shaders/d3d/sm30/InGameColormapPalInv.pso b/wadsrc/static/shaders/d3d/sm30/InGameColormapPalInv.pso
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index 99e874ec6..151312317 100644
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diff --git a/wadsrc/static/shaders/d3d/sm30/NormalColor.pso b/wadsrc/static/shaders/d3d/sm30/NormalColor.pso
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diff --git a/wadsrc/static/shaders/d3d/sm30/NormalColorPal.pso b/wadsrc/static/shaders/d3d/sm30/NormalColorPal.pso
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diff --git a/wadsrc/static/shaders/d3d/sm30/RedToAlpha.pso b/wadsrc/static/shaders/d3d/sm30/RedToAlpha.pso
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diff --git a/wadsrc/static/shaders/d3d/sm30/SpecialColormap.pso b/wadsrc/static/shaders/d3d/sm30/SpecialColormap.pso
index c1f4d8f35..5da15158e 100644
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diff --git a/wadsrc/static/shaders/d3d/sm30/VertexColor.pso b/wadsrc/static/shaders/d3d/sm30/VertexColor.pso
index 46e56db6b..46d2bc3d4 100644
Binary files a/wadsrc/static/shaders/d3d/sm30/VertexColor.pso and b/wadsrc/static/shaders/d3d/sm30/VertexColor.pso differ