[NTG-context] MkIV gray, no MkII black ?

Hi, in MkII I set \setupcolors[state=start] to activate defined colors (for text, numbers etc.), and \setupcolors[state=stop] to set these colors to black. Now, in MkIV \setupcolors[state=stop] does set these colors to gray. Not to black. [Log: "color : system gray is global activated"] What is the key to set either "color is color" or "color is black" again? Steffen