Is it possible to paint your watch gold? yes.
Is it a smart thing to do? questionable.
If you are good at spray painting you could do this.
It is possible that if your spray too much in the right spot, like around buttons, it could leak into the watch.
I would not suggest it because if you have issues with your watch it will void the warranty on your watch because you painted the watch, and looking up your serial number will show the color of the watch. If you don't mind voiding the warranty on your watch and you are really good at spray painting then you can go for it.
Personally, I would not do it.