Internally keep track of the value of the current color (issue #564)

src/modules/graphics/opengl/OpenGL.h

@@ -22,6 +22,8 @@
 #define LOVE_GRAPHICS_OPENGL_OPENGL_H
 
 #include "GLee.h"
+
+#include "graphics/Color.h"
 #include "graphics/Image.h"
 
 namespace love
@@ -42,6 +44,16 @@ void initializeContext();
  **/
 void uninitializeContext();
 
+/**
+ * Sets the current constant color.
+ **/
+void setCurrentColor(const Color &c);
+
+/**
+ * Gets the current constant color.
+ **/
+Color getCurrentColor();
+
 /**
  * Helper for setting the active texture unit.
  *