I am certainly no expert, but I would start with the darker shade and lighten instead of trying to darken. What paint products are you planning to use?
On second thought, I am withdrawing that comment. After thinking about it, I started with a gallon of white and added green until I got something I liked. If I wanted a couple shades darker, I would have added more green but not black.
Last edited by FriedGreenTmater; 03/29/2010 4:05 PM.