snake: the wand tool only works on contiguous part of the drawing on my version of PS.. for this, I think "color range"with no fuzziness works better.. otherwise, yes photoshop works , you 're right, just I don't feel to open PS just for this

(and I don't see the point of MS paint as I use promotion

) , thx anyway..

Akira, when I remove unused colors nothing happens because all colors are still used, so it doesn't remove anything.. when I press remove duplicate colors, it really removes the color from the palette, but all the pixels that indexed this color become black.. so actually Miascugh 's trick is the best,
Miascugh, thx, it works perfectly

I will stick to this method until I find -hear of - a faster one

I'm really surprised there is not an automatic way to do this action tho..
