If arg0str is used for a spotlight's color, convert that string to an int and pass that value as the light color. UDB's color picker interface uses the arg0str field for spotlight color.

src/level/doomdata.h

@@ -3,6 +3,7 @@
 
 #include "framework/tarray.h"
 #include "framework/templates.h"
+#include "framework/zstring.h"
 #include "math/mathlib.h"
 #include <memory>
 #include <cmath>
@@ -237,6 +238,7 @@ struct IntThing
 	short		flags;
 	int			special;
 	int			args[5];
+	FString		arg0str;
 
 	short pitch; // UDMF
 	float height; // UDMF

src/level/level_light.cpp

@@ -116,6 +116,15 @@ void FLevel::SetupLights()
 
 			// sun color
 			lightcolor = thing->args[0];
+			/*
+			// disabled for now, because I'm unsure if UDB will use the color picker interface for the sun color
+			if (thing->arg0str.Len() > 0)
+			{
+				FString hex = "0x" + thing->arg0str;
+				int rgb = hex.ToULong();
+				lightcolor = (uint32_t)rgb;
+			}
+			*/
 
 			// sample distance
 			Samples = thing->args[1];
@@ -306,8 +315,14 @@ void FLevel::CreateLights()
 		{
 			lightcolor = (uint32_t)thing->args[0];
 
-			// to do: UDB's color picker will assign the color as a hex string, stored
+			// UDB's color picker will assign the color as a hex string, stored
 			// in the arg0str field. detect this, so that it can be converted into an int
+			if (thing->arg0str.Len() > 0)
+			{
+				FString hex = "0x" + thing->arg0str;
+				int rgb = hex.ToULong();
+				lightcolor = (uint32_t)rgb;
+			}
 
 			innerAngleCos = std::cos((float)thing->args[1] * 3.14159265359f / 180.0f);
 			outerAngleCos = std::cos((float)thing->args[2] * 3.14159265359f / 180.0f);

src/level/level_udmf.cpp

@@ -224,6 +224,11 @@ void FProcessor::ParseThing(IntThing *th)
 		{
 			th->alpha = CheckFloat(key);
 		}
+		if (!stricmp(key, "arg0str"))
+		{
+			th->arg0str = value;
+			th->arg0str.StripChars("\"");
+		}
 
 		// now store the key in its unprocessed form
 		UDMFKey k = {key, value};