Same here. I used black Krylon Fusion on my AC500 intake, let it dry for several hours, and then hooked it back up. So far no problems and it blends nicely with my black background. You shouldn't have any problems.
krylon fusion is safe for fish, but eventually it will wear off in the water. I had to repaint some intakes I painted about 6 months ago. I always painted using 2 coats, 1 coat on, dried for 30 minutes and 2nd coat, air dried for 1 day, in a bucket of water for a couple more days, and air dried for another day, then into the fish tank. oh well it beats the blue and green(eheim)
I think the different colors are for the "challenged" folks. Intakes one color, returns another.
Makes it easier to follow the pictures I guess.
Fusion makes them easier to use, especially if you like "all the same", anal or not.
Everything in my tank gets shot with black Fusion if it's not already black.
Anything else looks like a sore dic*.......thumb sticking out IMO.