Dry pigments work well though I find the colors to intense. I have made two small batches of epoxy and filled them with two different colors of wood powder to a dough consistency. swirled the two batches together made the repair. after sanding I got a grain like appearance under the finish.
I have tried the two-batch swirl method a couple of times but without a lot of success. Probably need to practice a little more. Re the intensity of dry pigments, you are correct, and the addition of wood powder does mitigate the color of the pigment. Another approach is to use dry pigment for the color you want, and then adjust the intensity of the mix with tiny amounts of the epoxy pigments sold in the stone trade. Paste pigments are available in small tubes (or large tubs) in a variety of colors from pure white through black, including shades of beige and brown to mimic natural stone. Don't use universal tint colors from the paint store because those will interfere with the epoxy cure and the results are not entirely predictable. I have also tried some solvent-based dyes that are often used for epoxy joints in granite counters, but have not been satisfied with the results in some of the epoxies that I prefer, probably because I am working with such small batches that it is impossible to get consistent mixes. In large batches, the results have been pretty good.
