Try Lt. Brown from Berrywell/Augenblik. About 7 minutes should do it. You can buy from Stephanie Laynes at Smooth Skin Supply - http://www.ssmoothskinsupply.com/librcrti5.html . Great waxes, too!
I usually just use light brown or medium brown on my blonde clients and just halve the processing time. I am partial to Intensive Lash and Brow Tints, but I have had pretty good results with almost every tint brand I've tried. I would not recommend Roux though, they just don't have a wide enough selection of colors.
If the brow tint ever comes out too dark, do what cosmetologists do for lightening a dark color job by using a soap cap! Mix equal parts brow developer with clarifying shampoo (any will do, you want something somewhat harsh that will strip color, I've even used Dawn dish soap in a pinch) leave on for a minute and remove.