Elements 11 selective layer question

[Iceax]

Evening all

I know these are love hate and i very rarely do them but im trying to edit an image and im struggling.

So i open image, create a adjustment layer, drop teh saturation and i can brush the colour into the layer.

however should i unclick the mouse and brush over my layer again i loose the colour and it drops back to b&w.

Im sure this is a really simple setting but im pulling my hair out over it.

Can anyone advise what to change.

Thanks

Andy