My users have been yearning for this, and I've searched both here and on vB.org but to no avail.

I apologise if this comes under the category of some other hack or (far more likely) template modification, but I've searched under a fair number of terms and not seen anything.

I know a version of this existed for vB 3.0.x, although it was faulty and although it appeared in Edit Profile for users, it could only actually be enabled when the section was edited by a staff member.

Thanks a ton if anyone can. I'm getting quite a lot of aggro about this. For some reason, my users really seem to like their individual colors. :p

Just add a custom profile field with a bit of regex to check it and then wrap the post text in <div style="color: #{$post[fieldX]};"></div>. Of course changing the X to the number of your field.