I wouldn't do it myself... I have a Buck-184 that someone painted black and the paint is comming off and it just looks ugly... Of cource, I got the knife for a good price because the fool messed up what would have been a really good knife by painting it...
But, it is your knife and there are lots of finishes out there... I wouldn not expect the blade to remain painted however unless you find a really tough finish and I am not sure I am qualified to give a suggestion.
Also, I moved your Sale post... these need to be kept in the classifieds area so that you can mark it sold and such without affecting the other forums...
See:
http://www.quarterbore.net/forums/sh...=1850#post1850
Also, you might consider looking for an M-9 Bayonet if you want a black blade... Much cheaper and you won't regret messing up your knife later!