If you paint the bottom half of the lip black and the side skirts black then what about the rear. If you don't tie it all together then you may look like a Honduh with an unpainted body kit.
I can see it now, " Hey look at that red Protege, but too bad he didn't finish painting the body kit."
So my vote is to paint it all red unless you have other body parts painted black to tie it all together. Such as the center of the hood blacked out, blacked out headlights, gloss black rims & the lower section of the rear bumper could be blacked out too.
Just my $0.02