Is there any light sources that could be coming through the paint on the tank, making it look grey?
When I paint my tank backs, I keep adding coats until I can't get a flashlight beam through from the inside of the tank.
Anyways, I'm curious to see if anybody knows what might cause this...
No, dark behind it.
The only thing I can see that is causing it are very bright lights right above it. In the past when I've seen this the lights were running lengthwise down the tank (as are mine) and the painted side was the back, parallel to the lights. Mine is the end, so there are a pair of fixtures shining light directly down onto the side.
With a bit of trepidation I took some really black, glossy oil paint (rustoleum) and painted a small portion this morning. After drying it was very slightly darker, but it also looked grey.
I can only assume it's something about the light, the glass, the angle, etc.
So I rolled the whole side this evening, waiting for the first coat to dry (it's pretty thin, I can see a lot of light looking in toward the tank). But it looks fairly evenly grey from the other side.
But it really bugs me how grey it looks. However it's not that noticeable if one just walks up to it, and it hides the plumbing and frame.