Ok, I have a feeling i'm gonna be laughed at and called an idiot, so I'm just saying that I understand that you're talking about a web page that you're designing. if no - oopsi!
(by webpage I also mean documents, no matter what format, PDF, DOC or even JPEG)
Well, first piece of advice, this isn't the answer, but still: are you sure you want a black background?
please have a look in this site:
Color Psychology — Infoplease.com
Make sure that the background color (a very dominant color) that you want is black, instead of any other of those things.
As for the answer:
I think that the color less matter, but how you actually do it, the effects. for example: do you use a cheap bevel? do you use reflections? do you make aqua? do you combine shining it? those kind of stuff are the real question, I think.
Gray is great. depends on your style, my style would be maybe toxic green, with bubble reflection, kinda aqua thing. I'm really attracted to those clear-shine-and-reflections style
don't even know why
Another piece of advice that I can give:
Don't invent the wheel. go to google and search for well-done expert and pro designs!
I'm not saying to copy them, I am saying to get inspiration (did I write it right?:S), and ideas.
When I first learned CSS for web pages, I was terrible!!! I couldn't do anything, it made me angry and frustrated, that other people make such amazing stuff, and I can't make a subtitle to the side of the title! it was terrible.
So I thought, maybe I'll RE-DESIGN webpages! I started making a new google (without the programming stuff, of course, just the style). and guess what? I'm much much better! my computer filled with folders like "RD - Google" (RD as for Re-Design).
really good idea. Why am I mentioning it here? I think every designer, no matter what he designs should do the same, even taking a pause from his current projects, to re-design what experts and pros did, and than you come back with their knowledge!
Good luck! sorry for the long message