small refactor

shader/instancing_fragment.glsl

@@ -1,8 +1,9 @@
 #version 330
 
-uniform vec4 colDiffuse;
+in vec4 fragColor;
 out vec4 finalColor;
 
 void main() {
-    finalColor = colDiffuse;
-}
+    // Advanced coloring. CG lecture really paying off now
+    finalColor = fragColor;
+}

shader/instancing_vertex.glsl

@@ -1,10 +1,14 @@
 #version 330
 
-in vec3 vertexPosition;
-in mat4 instanceTransform;
+layout(location=0) in vec3 vertexPosition;
+layout(location=1) in mat4 instanceTransform;
+layout(location=5) in vec4 instanceColor;
 
 uniform mat4 mvp;
 
+out vec4 fragColor;
+
 void main() {
+     fragColor = instanceColor;
     gl_Position = mvp * instanceTransform * vec4(vertexPosition, 1.0);
-}
+}