Ford Blue. This color by Easwood seems to work well for most people.
I was using Harbor Freight Red. I was having trouble and tried a lot of different techniques without satisfactory results.
I use the Eastwood Ford Blue in a Frankford Arsenal vibrating tumbler. I add a couple spoons of powder and a hundred or so bullets. I tumble for 30mins. Pour bullets in a mesh of some sorts. Shake mesh basket over paper to remove excess powder (save and reuse powder). The amount of powder is not exact. You just use more powder than needed. I get great results with this method.
I don't care about color. I just want it to work.