I admit that it might not the most used feature of all - but it's possible. First I started with all the explicit constructors and comparison only for the same type. And at one point I asked myself, why should the comparison be limited? Yes, the chances are good that the alpha channel is not fully set. But does it hurt to implement the two comparison methods? No. Does it help the user and provide a consistent API? Yes.

Actually I'd love to add `cocos2d::extension::HSV` into the compare- and convertible mix ... ;)