I faced that problem too with my bareminerals, so I had to go for the lighter of the two that they sent, when I thought the first one would match just fine.
BTW isn't this foundation mineral a nockoff of bare minerals?
Cosplay list for 2013
Code Geass - C.C R2 Uniform 100%
Code Geass - C.C Empress Dress 10% - Pattern all drafted
Carmilla Formal Wear (OC for Sidereus) - 5%
Sister Lilly (Cast Character for Sidereus) -5%
Anime Boston 2013 - With Harbinger Entertainments and Sidereus Live Action Roleplay