I did something similar , but I still have the use of my normal white interior lights.
What I did was while I was running a switched/ground wire up to the area above the rear view for my radar detector, I made use of the power I ran and added some blue LED's for some ambient lighting.
They look cool and cast a nice cool-blue glow all over the cockpit but at night it does not effect your night vision but you can see everything like cup holders or what ever you may be looking for, it even makes the non-lighted buttons on the homelink mirror easy to see at night.
The other cool side effect is the way that the light fades into view when the regular interior lights dim after closing the door, they kind of just fade from white to blue with a little bit of purple thrown in.
I did not do a DIY, but I can describe it easy enough...
1st-you need to run a switched power wire as well as a ground up to the the overhead panel.
The panel is easily removed by 2 Phillips screws inside the sunglass holder.
I got switched power from the fuse box and used the old wire-tuck behind the fuse method (I used the fuse for the heated seats since mine are not utilized) and ground screwed with a self-tapping screw, ring terminal and star lock washer onto the dash bracket.
I ran the wire up the A-pillar and tucked it behind the head liner.
I got the LED's from Pep-Boys, a pack of 3 for 6.99. I removed the light panel and drilled 2 9/32 hole for the the LED's (they are the type that snap locks into a pre-drilled hole)
I drilled the holes in the rear corner area in the black plastic housing and pushed them into the holes so they were facing towards the front of the car but inside the light housing right next to the regular white lights.
I then just tucked the wires in (after I connected them to the wire I ran up) and re-installed the panel.
The lights come on any time the ignition is on, but you could install a switch if you want to be able to turn them off, but since they are LED's there is no heat so that's not a concern.
I will try and post some pics and maybe move this to it's own thread if there is any interest.
Diode Dynamics offers some really nice kits with various stages of intensity increase as well. I can't personally vouch for their stuff but other people in the community have had good luck with their stuff. I know once I get around to doing cosmetics I'll probably use some of their stuff to change out the OEM stuff.