Dark brown or sand in the beginning
The Domke bag was always offered in 2 colors: dark brown or sand. Many felt sand would keep the gear/film cooler and safer, but for the photojournalist the darker brown didn't call attention to them. And it also fit in with blue jeans or business suit. (The canvas isn't abrasive to slacks, but over time it will fade and not look as nice with a suit and tie as it did when it was new.)
Navy was added for those who wanted something that didn't look as "outdoorsy" or rugged. They all had the same sand trim and straps.
I waited to add black, because I felt it would be harder to find things inside the bag and it meant that I could no longer use the same color webbing on all the bags!