If you go here:
http://www.sephora.com/brands/bare-escentuals/static.jhtml?brandId=Bare+...

It will open the BareEscentuals Page from Sephora. There is a shade finder that you can look through. There is an especially dark shade that you might match called 'Deepest Deep'. A starter kit is roughly $60 but once you run out of anything, each tin is approximately $25 maybe a little less. It has great coverage and blends in great. Totally worth it in my opinion if you want flawless skin.

There's also a product that goes on white but changes to your skin tone. It's Revlon Beyond Natural Skin Matching MakeUp. It works great and has 5 different shades. You could possibly try the darkest one. I'm betting that they sell it at most drugstores for approx. $10. For more information go to http://Revlon.com.

I have the opposite problem -- I'm abnormally pale. lol I've found that DermaBlend Reflections (which you can buy from any DermaBlend retailer but I suggest checking on e-Bay...you can get brand new product for a fraction of the price) and mineral make up (I use ones by Fyrinnae and Femme Couture) seem to be the most forgiving. They blend and adjust, so as long as you get in the ball park, they'll pick up the slack. I know Femme Couture has some darker shades and since Fyrinnae hand produces their products, I bet they could come up with something custom. They're super affordable, too. Only downside is they have a slow turn around. But, being a small company making every batch by hand, 2-3 weeks isn't too big a price to pay.

but I have a darker complexion.

LOreal True Match @ Target for $5.

It's works for me.