I use black and blue, depending on the tank. Black shows more color in plants and fish, but blue makes the tank look bigger. Show's more depth.
White will show ALL of the dirt in the tank, and all the algae growing on the wall. IME, back walls are hard to clean because of plants, pipes, tubes, etc. You would want something that would hide algae.
In my 40, I have a black background, mostly to show off my fish. I have black gravel, black slate, and a black background. As far as fish go, I have Psuedotropheus saulosi. Males are blue, females are golden yellow. It's my display tank in my room, so I wanted the fish to pop.
In my 29, I have a black background, because it shows all my plants really well. The fish show up well too. The gravel is a reddish color. This tank is in front of a window, so when the sun shines on it, the blue on the backside of the black background shows through a bit, so my background shows a hint of blue in it, which is pretty cool.
In my 16 bow, I have blue, because it has fake plants in it, so I wanted most of the color to come from the fish, which the blue helps with. I have glo danios, harlies, gouramis, etc. in it. I haev alot of reddish fish, and red and blue goes very well together IMO.
On my 20 long, I have a reflective silver background. It's like a mirror, so it reflects a bit of light, but it has my N. multifasctatus in it, and no plants, so it really doesn't matter much, but I would never have this color on a planted tank.
My friend has a blue background on her planted 29, and it looks really nice.
When I set up my 20 long shrimp tank, I'm prolly gonna use black, just cause it'll show the reds and blues in the shrimps I'm planning on getting really well.
65 gallon low tech planted