Not sure if it is what you are looking for but
once you get two colour layers you can try the LCH Chroma 'layer mode' (you will find this menu just above the layers dock ((LCH Chroma is near the bottom of the list)) and lessen the opacity as you want.
once you get two colour layers you can try the LCH Chroma 'layer mode' (you will find this menu just above the layers dock ((LCH Chroma is near the bottom of the list)) and lessen the opacity as you want.
