Another trick to the newlighttable and newdarktable.
Open up your favorite image editor (I use Fireworks MX).
Make a rectangle and give it the same fill color as darktable.
Edit the fill color and bring up a slider to adjust the color. Move the slider down a few "notches" until you have something a little lighter than the darktable color (you may have to go the other way if darktable is too light). Note the ASCI code for the color you just created (it will be your newdarktable).
Repeat the process, only this time start out with the lighttable color as your fill. This one will be newlighttable
You now have two new colors to use for newdark and newlight table that won't clash with the existing light and dark table colors.