I have been dyeing lots and lots of darks lately for a geometric I have been hooking away madly on. These above colors Licorice and Republic Red are dyed over textures with formulas from Susan Quicksall's book Dyeing For Color. Check out her website Hollyhilldesigns.
These darks do a wonderful job of showing off the lights and mediums....contrast of value is what it is all about in geometrics. I will post a photo soon of my progress.