fix missing morphtarget color attribute (#16738)

There's one color attribute declaration that is missing and will cause
an error.

---------

Co-authored-by: Kevin Blackburn-Matzen <[email protected]>

Author: kmatzen

packages/dev/core/src/Materials/materialHelper.functions.ts

@@ -192,7 +192,7 @@ export function PrepareAttributesForMorphTargets(attribs: string[], mesh: Abstra
         const tangent = manager && manager.supportsTangents && defines["TANGENT"];
         const uv = manager && manager.supportsUVs && defines["UV1"];
         const uv2 = manager && manager.supportsUV2s && defines["UV2"];
-        const color = manager && manager.supportsColors && defines["COLOR"];
+        const color = manager && manager.supportsColors && defines["VERTEXCOLOR"];
         for (let index = 0; index < influencers; index++) {
             if (position) {
                 attribs.push(Constants.PositionKind + index);

packages/dev/core/src/Shaders/ShadersInclude/morphTargetsVertexDeclaration.fx

@@ -19,7 +19,11 @@
 		#ifdef MORPHTARGETS_UV2
 		attribute vec2 uv2_{X};
 		#endif
+
+		#ifdef MORPHTARGETS_COLOR
+		attribute vec4 color{X};
+		#endif
 	#elif {X} == 0
 		uniform int morphTargetCount;
 	#endif
-#endif
+#endif

packages/dev/core/src/ShadersWGSL/ShadersInclude/morphTargetsVertexDeclaration.fx

@@ -19,7 +19,11 @@
 		#ifdef MORPHTARGETS_UV2
 		attribute uv2_{X} : vec2<f32>;
 		#endif
+
+        #ifdef MORPHTARGETS_COLOR
+        attribute color{X} : vec4<f32>;
+        #endif
 	#elif {X} == 0
 		uniform morphTargetCount: i32;
 	#endif
-#endif
+#endif