Sure, I wouldn't mind it for his classic outfit, but...
Obviously his blue, green and red colors can't go (two of which are based on characters. red - Mario. blue - Captain Syrup.) can't go, that means his Gameboy and "sailor" (what I'd like to call it) colors are what it would replace, but I'm personally fond of both (Gameboy color is my go-to for the classic outfit), so I'd rather not see them go.
Then again, I just remembered team colors aren't a thing anymore, but I don't think green should be replaced, for tradition's sake. Waluigi color is more perfect for Luigi imo. Green and "sailor" Wario aren't based on anything, but they look great. EDIT: Though you could argue the green color is based on the green color scheme the Gameboy screen used to have.
I think Wario has very solid color options, both Warioware and Wario Land costumes. Though, I wouldn't mind a purple/pink color scheme for his Warioware costume, referencing Wario-Man, regardless of it being his final smash.
Personally, I just want Wario's design to be updated. He looks TOO stubby and deformed in Brawl. I think Wario never really translated properly to 3D because he looks best in 2D, but I think Smash could do it provided he doesn't look deformed again. I want him taller and much more toned.