I have made an online tool to translate colors from a photo to acrylic and oil color mixes.
This program let's you work with confidence in all light conditions.
You can use it for extremely precise mixes but also just to help inspiring you with which pigments to use.
I hope you will enjoy working with it.
You can use the tool on this web site:http://sensuallogic.com/paintmaker/OnlinePaintMixer.html