Well it's more that Kuro, straight out, is the literal shade of black. It's the description of black. Kuroki (which is what is in the title) is to be feeling (a state of) "black(ness)" and isn't a description of the colour at all, which is why it is better translated to dark in english. Translated as just black is painfully blunt and drops the meaning altogether. Same goes for Shiro/Shiroki for the second title.
Considering these were the original translations we were using here on PokeBeach, I'm just a little perplexed at the very blunt and loose translation being used now.