I assume you're talking about a new purchase ...
If so - it's been decades since I knew of anyone deliberately considering a different color topper / canopy (unless that was the only option they had ...).
If you care about 'appearances', I'd definitely say get the white top to match the truck.
If you get the black one, people will think:
(a) you got the black one new only because it happened to be in stock at the dealer or you got a better price on it or you were just too impatient to wait on a color-matched one
OR
(b) you got the black one used to save money and you don't care about looks
I'm *not* saying this should necessarily matter to you. I'm only saying that's the impression observers will have ...