Making a Rainbow haired girl for VV3 isn't impossible by any means; it would just be time consuming more than anything else.
Because the heads are different sizes, it would require resizing, which really isn't hard. I don't think it would even effect the quality, because the VF heads would be sized down = no over-sized pixels. The tricky bit would be that each picture would have to be lined up by hand. I would work on it (albeit off and on, so it would take a little while), but I haven't got VV3, so I don't have the original head pictures to edit. Sorry!
--
Xay was kind enough to send me the files for VV3 female heads, so now my question is this: which head do you want me to replace in the VV3 game with the rainbow head? Is there one in particular? Let me know and I'll get to work on that.
_________________________
And what if it makes you laugh now but you cry as you fall asleep?