My local store only has red, green, yellow, blue coloring powders. No brown or anything that looks like chocolate.
How to make chocolate-brown from these basic colors?
I tried cocoa powder, but that changed the texture and the macarons failed.
A French recipe suggests 1 green for 5 red, resulting in pink that supposedly becomes brown when cooking, but that is with liquid colorant so not sure it applies.
Best Answer
I wouldn't try to mix food coloring for something as sensitive as macarons and a color as difficult as brown. Color theory sounds easy enough, but practice is a different beast. The intensity of the pigments varies, there are unexpected interactions, etc. And then you need some solid theoretical and practical background in working with color.
That is not to say that you cannot be successful just trying any likely-looking ratio, but the chance that you get the color you were aiming for instead of some drab mud color is not so good.
Unless you are willing to invest the time and effort needed for several macaron batches doing the R&D (and we can't do it for you, or report to you based on previous experience, because we don't have the exact powders you have), you are better off going some other route.
If you absolutely need to go with your powders, the usual process of discovering the correct ratio is following:
If everything went well, you now have the color you wanted. If not, you have to repeat until you get consistent results.
A shorter form may work for you, where you start with a random ratio (why not the 1:5 you found somewhere?) and use a Newton method for finding a color good enough for you. Don't forget that the steps will still need to accommodate a nonlinear relationship between pigment amount and perceived color, so if you are looking for a color halfway between the effect of 1:4 and 1:64, it's not 1:34, it's 1:16. You will still need to bake several batches in succession, so it may be more work then doing a lot of batches at once. Anyway, I think you see now why I suggested buying the premade color.
By the way, what I outlined is an already abbreviated method, giving you only one "line" of hues achievable with your colorants. The full method would require you to make a whole color triangle. It is entirely possible that the color you want is not on the straight line between your red and your green, but requires also some yellow or some blue. Or that it is completely outside of the color space of your pigments, so not achievable with that brand.