colour tool does not allow black and white

[jj22]

i have already eyedropped black / white . But once i clicked on the image, grey appears . i'm in the mode of RGB colour. It only doesn't work for black and white. I've tried with red , blue , etc and they all worked. Just not black and white. i'm really frustrated 

[hatstead]

Exactly what are you trying to do?

Is the image open in Editor, Expert tab?

Have you made a selection of the object intended for the color change to b/w?

[Greg_S.]

. . .  and exactly which tool are you using?