Hi Eelover,
I have the same problem trying to pick colors. However I did find one that is great for all over color, BM Muslin. I also had a 50% version done for the wall above my chair rail in the DR.
I am using most of the "pop" of color in rugs, accessories and window coverings. I can suggest that if you find a color you like but feel it is either to dark have them do it at 50% and the same for to light, 50 or even 25% darker. You can create some beautiful colors like this.

Choose a simple neutral default color. BM Manchester tan, edgecomb gray or revere pewter are good ones. How much is your painter charging for extra colors? It might be worth it if you know you want a room to be a certain color, but if you're not sure just go with the neutral for now. BM gray wisp is a nice second color in the gray/green/blue family and should go well with the above neutrals.

The link below may be of interest. Once there, follow the link "Best Room Paint Colors for Dark Rooms" (near the bottom of the page) for more info.

Here is a link that might be useful: Paint and LRV