Two things come to mind when I read this post:
1)  Black is not always "black" - varying shades - you may want to paint the whole door so it matches!
2)  Where are you thinking of putting your bike rack?  If on the rear bumper - you may want to reconsider that option!!!!!  There are many posts/threads about bumpers falling off due to the weight/bouncing of the bikes!!!  If this is where you want to mount it - you may want to have it welded to the frame BUT then you take weight off your tongue, which now may cause a different problem for you!