rewrite gnColor to be C compatible

src/types/gryphn_color.h

@@ -1,3 +1,6 @@
 #include "../math/gryphn_vec4.h"
 
-typedef gnMultiType4<int, int, int, float> gnColor;
+typedef struct gnColor {
+    int r, g, b;
+    float a;
+} gnColor;