At a guess- [I always used black sparingly time-wise but that was on both system and growing] 1b is one step up from black..it shows the brown hue under strong natural lighting conditions..tends to look almost black under ordinary artificial light [flourescent can make any color look `odd`] as you are applying to your growing hair only, try the intense dark brown and leave it on for 5-10 minutes and see how it looks...these coloring products can be a bit like finding a tape or glue you can `work`with ..can be a case of try one and see how you go with it. You may find over time -when oxidation sets in on your system, that you`ll use it on that too,so getting `used`to using it now should stand you in good stead-- Paul.