diff --git a/binaries/data/mods/public/gui/common/color.js b/binaries/data/mods/public/gui/common/color.js
index bf57d08797..2387c37bf3 100644
--- a/binaries/data/mods/public/gui/common/color.js
+++ b/binaries/data/mods/public/gui/common/color.js
@@ -34,7 +34,7 @@ function guiToRgbColor(string)
 		"r": +color[0],
 		"g": +color[1],
 		"b": +color[2],
-		"alpha": color.length == 4 ? +color[3] : undefined
+		"a": color.length == 4 ? +color[3] : undefined
 	};
 }
 
diff --git a/source/gui/scripting/JSInterface_GUITypes.cpp b/source/gui/scripting/JSInterface_GUITypes.cpp
index 33ec29fad1..cebc25e7a1 100644
--- a/source/gui/scripting/JSInterface_GUITypes.cpp
+++ b/source/gui/scripting/JSInterface_GUITypes.cpp
@@ -22,7 +22,6 @@
 #include "ps/CStr.h"
 #include "scriptinterface/ScriptInterface.h"
 
-/**** GUISize ****/
 JSClass JSI_GUISize::JSI_class = {
 	"GUISize", 0,
 	nullptr, nullptr,
@@ -127,79 +126,7 @@ bool JSI_GUISize::toString(JSContext* cx, uint argc, JS::Value* vp)
 	return true;
 }
 
-
-/**** GUIColor ****/
-
-
-JSClass JSI_GUIColor::JSI_class = {
-	"GUIColor", 0,
-	nullptr, nullptr,
-	nullptr, nullptr,
-	nullptr, nullptr, nullptr, nullptr,
-	nullptr, nullptr, JSI_GUIColor::construct, nullptr
-};
-
-JSFunctionSpec JSI_GUIColor::JSI_methods[] =
-{
-	JS_FN("toString", JSI_GUIColor::toString, 0, 0),
-	JS_FS_END
-};
-
-bool JSI_GUIColor::construct(JSContext* cx, uint argc, JS::Value* vp)
-{
-	JSAutoRequest rq(cx);
-	JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
-
-	ScriptInterface* pScriptInterface = ScriptInterface::GetScriptInterfaceAndCBData(cx)->pScriptInterface;
-	JS::RootedObject obj(cx, pScriptInterface->CreateCustomObject("GUIColor"));
-
-	if (args.length() == 4)
-	{
-		JS_SetProperty(cx, obj, "r", args[0]);
-		JS_SetProperty(cx, obj, "g", args[1]);
-		JS_SetProperty(cx, obj, "b", args[2]);
-		JS_SetProperty(cx, obj, "a", args[3]);
-	}
-	else
-	{
-		// Nice magenta:
-		JS::RootedValue c(cx, JS::NumberValue(1.0));
-		JS_SetProperty(cx, obj, "r", c);
-		JS_SetProperty(cx, obj, "b", c);
-		JS_SetProperty(cx, obj, "a", c);
-		c = JS::NumberValue(0.0);
-		JS_SetProperty(cx, obj, "g", c);
-	}
-
-	args.rval().setObject(*obj);
-	return true;
-}
-
-bool JSI_GUIColor::toString(JSContext* cx, uint argc, JS::Value* vp)
-{
-	UNUSED2(argc);
-	JS::CallReceiver rec = JS::CallReceiverFromVp(vp);
-
-	double r, g, b, a;
-	ScriptInterface* pScriptInterface = ScriptInterface::GetScriptInterfaceAndCBData(cx)->pScriptInterface;
-	pScriptInterface->GetProperty(rec.thisv(), "r", r);
-	pScriptInterface->GetProperty(rec.thisv(), "g", g);
-	pScriptInterface->GetProperty(rec.thisv(), "b", b);
-	pScriptInterface->GetProperty(rec.thisv(), "a", a);
-	char buffer[256];
-	// Convert to integers, to be compatible with the GUI's string SetSetting
-	snprintf(buffer, 256, "%d %d %d %d",
-		(int)(255.0 * r),
-		(int)(255.0 * g),
-		(int)(255.0 * b),
-		(int)(255.0 * a));
-	rec.rval().setString(JS_NewStringCopyZ(cx, buffer));
-	return true;
-}
-
-// Initialise all the types at once:
 void JSI_GUITypes::init(ScriptInterface& scriptInterface)
 {
 	scriptInterface.DefineCustomObjectType(&JSI_GUISize::JSI_class,  JSI_GUISize::construct,  1, nullptr,  JSI_GUISize::JSI_methods,  NULL, NULL);
-	scriptInterface.DefineCustomObjectType(&JSI_GUIColor::JSI_class, JSI_GUIColor::construct, 1, nullptr, JSI_GUIColor::JSI_methods, NULL, NULL);
 }
diff --git a/source/gui/scripting/JSInterface_GUITypes.h b/source/gui/scripting/JSInterface_GUITypes.h
index c6e47473e9..d23c0c8557 100644
--- a/source/gui/scripting/JSInterface_GUITypes.h
+++ b/source/gui/scripting/JSInterface_GUITypes.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2018 Wildfire Games.
+/* Copyright (C) 2019 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -31,8 +31,6 @@
 	}
 
 GUISTDTYPE(Size)
-GUISTDTYPE(Color)
-GUISTDTYPE(Mouse)
 
 #undef GUISTDTYPE // avoid unnecessary pollution
 
diff --git a/source/gui/scripting/JSInterface_IGUIObject.cpp b/source/gui/scripting/JSInterface_IGUIObject.cpp
index 2054a85cf5..2fe1a0fdaf 100644
--- a/source/gui/scripting/JSInterface_IGUIObject.cpp
+++ b/source/gui/scripting/JSInterface_IGUIObject.cpp
@@ -168,21 +168,7 @@ bool JSI_IGUIObject::getProperty(JSContext* cx, JS::HandleObject obj, JS::Handle
 		{
 			CColor color;
 			GUI<CColor>::GetSetting(e, propName, color);
-			JS::RootedObject obj(cx, pScriptInterface->CreateCustomObject("GUIColor"));
-			vp.setObject(*obj);
-			JS::RootedValue c(cx);
-			// Attempt to minimise ugliness through macrosity
-#define P(x) \
-	c = JS::NumberValue(color.x); \
-	if (c.isNull()) \
-		return false; \
-	JS_SetProperty(cx, obj, #x, c)
-
-			P(r);
-			P(g);
-			P(b);
-			P(a);
-#undef P
+			ScriptInterface::ToJSVal(cx, vp, color);
 			break;
 		}
 
@@ -539,21 +525,12 @@ bool JSI_IGUIObject::setProperty(JSContext* cx, JS::HandleObject obj, JS::Handle
 				return false;
 			}
 		}
-		else if (vp.isObject() && JS_InstanceOf(cx, vpObj, &JSI_GUIColor::JSI_class, NULL))
+		else if (vp.isObject())
 		{
 			CColor color;
-			JS::RootedValue t(cx);
-			double s;
-#define PROP(x) \
-	JS_GetProperty(cx, vpObj, #x, &t); \
-	s = t.toDouble(); \
-	color.x = (float)s
-
-			PROP(r);
-			PROP(g);
-			PROP(b);
-			PROP(a);
-#undef PROP
+			if (!ScriptInterface::FromJSVal(cx, vp, color)
+				// Exception has been thrown already
+				return false;
 			GUI<CColor>::SetSetting(e, propName, color);
 		}
 		else