Recolor SD1.5

Quite a simple workflow. You can do the tagging with another node if you like, or do it manually... I use a gamma node to boost the recoloured images , you can adjust it for your preference.

The recolored images are slightly blurred and than multiplied in layer colour mode, so no information of the bw original is lost.

Couldnt get it to work in SDXL. So this is the way to go, unless a working control net for SDXL is released....

Epicrealism is quite good as a checkpoint for the purpose....