Same color chooser window for all platforms + apply button

I make one PR because these 2 commits comes together for me :
+ Only one window = apply button for all systems.
(Add a feature to just one platform isn't good no ?).
+ One-window-to-rule-them-all : easier to maintain.

Can't find where is define CHOOSECOLOR and ChooseColor()... ??

Signed-off-by: bestel <steven.valsesia@gmail.com>