[Edit: can you all see these pics? Or did I make them private...]
I will agree and disagree on just going light colors or dark colors. I feel it still has more to do with a theme to follow. If the outside is purple, a charcoal interior may just the wise selection over the complimentary yellow. (the way I remember the compliments are Christmas [red/green], Easter [purple/yellow], and the Dolphins [orange/blue]).
Before I go on, let me give a reference:
The color may not be bold, but it works perfectly for the theme. It's a metallic base (DuPont Chromabase '03 Mitsu' Titanium) that looks dark until light hits it...then it looks very sharp. The outside is orange and I'm working on carbon fiber pieces still for the interior...so it all kinda works together. So, dark can be made to play with lighting as well. Parts of the drive rails are orange (good ol' hugger orange) and I'm glad I didn't keep the orange going throughout the interior. Which brings up another color topic...
Dual colors are really pleasing to the eye when in one area. The exterior being one bold color can be made even better by adding a second as an accent. The interior can also use this to enhance the feel of the guts, and make probably the most neglected area now worth looking at. Go back to that shot I posted, and compare it to plain interiors...maybe it's something the camera can't capture, but it works together with the color and the hardware where the inside is just eyecatching and fun to look at...and that's without one single mind-numbing blinking LED or CCT (which is a cheap get-off IMO).
Like the others are suggesting, take your hardware into account as you choose a color. I have a lot of chrome (rad, powersupply, fittings, and memory) and are nothing more than accents and not over done IMO. It's put together now, and I feel great that I've captured the theme of a vehicle and not just a modded case full of gadgets. The Titanium color choice was perfect, and I'm not sure if any other color would have pulled it off. Sure, I could have just gone wild and picked a wild-ass color, but what would be the point by venturing off-theme? "Hey...look at me! I'm yellow!" Great...
Now, when painting the guts...don't just spray the piss out of it and call it done. Take into account what needs painted and what doesn't. First, consider the ground loop to keep everything in the ESD circle. The posts on the mobo-tray shouldn't be painted over, nor should the PCI area. If you paint these areas, you'll be isolating the part from the chassis ground loop.
I taped off an entire section for the tray, but that was just because I knew I wouldn't see any of it in the end (even that bare area to the right is covered by either the crossflow fan or soon to be a carbon reservoir). If you want to paint the tray, I'd either suggest taping off a square like I did or find the little round stickers used for labeling and put a dot over each post. When you're done painting and it's dry, peel 'em off and all your posts are left with bare metal...and it's done with uniform circles.
Also take a peek at the PCI area where I just taped off the entire area, minus a strip of the PCI land that won't be covered by the card slots. I just used the slot covers as a reference, then taped off about 1/16" under there. So, once all the cards or covers are on, you can't see the bare metal but there's still a good contact area. Also, I've left a strip around the PS mounts on the rear.
Just don't neglect the fact that the computer you're modding has basic needs to survive.
Another comment on planning and execution of painting: visualize and plan where painting will stop and start.
1) if you'll never see it when it's assembled, don't bother painting it. Mask it off. I say mask it as a sharp line is always better than that overspray that could get noticed. I missed this with the rear of the other panel, and didn't notice until I was done. Perhaps some day I'll get it painted as well, but right now, it's the bare metal and barely gets by with me. It's pretty much covered up with all the hardware and such bolted in...but I know it's there and I notice it (it's less obvious that those pre-build pics)
2) I could have just painted the case's interior and called it good. But, the edges needed a color too, so the entire chassis ended up getting a coat. Not just that, but I also carried the color to the rear. It works for me, but may not for you. People may never get a close look at the rear of your case, but I like paying attention to the details and feel better knowing I did this at 120%.
3)paint has a dimension to it that you can't get around. If there's an area that has a tight tolerance or has parts moving in and out, then it's best to leave it bare somehow. My drive cages fit both of these ideas as they use drive rails that are already tight and adding a couple mils of paint will make it REAL hard to get anything in there. Also, hard drives and opticals will get installed and removed so the paint will wear over time and eventually get ugly. See #1..you only see it with hardware removed, so leave it as it is.
Anyway...that's a huge post and I'll leave it at that. But in order to get our opinion on color will make it our mod. If we hate your decision on UV reactive pink or whatever...that's cool because it isn't ours. Hell, people that hate orange and tried to sway me from the color now think otherwise in my case (no pun), and the execution or a theme pulled it all off nicely.