My color matching spreadsheet.
https://dl.dropboxusercontent.com/u/16294011/color_mixing.zip
Maybe a bit of overkill, but it works very well. I mix creatix paints by the drop, stir with a match stick, then swab directly on the sheet. Once they dry I compare to the playfield and go from there. Once I have an exact match I can make any amount I need, b/c I have the formula! I can mix it in my airbrush while I'm spraying, so I never run out...
Dan