[Dabhand16]

There is more than one way to skin a rabbit.

Easiest way is to copy the layer and desaturate the copy to give a mono image. Then use a layer mask to reveal the underlying colour you want to show. Use black to bring out the colour, and if you go wrong, change to white and you can put back the mono.

You could also use two layers, desaturate the top one and use the eraser in the same way, but it is not so easy to correct any errors.

I think there are other ways too, but these will be the easiest.