Little Red Riding Hood is looking slightly too yellow, so I add a new Color layer. Then I pick a red tone and start to paint on her skin to remove some of that yellow. I still want to keep some of it, so I reduce the Opacity, which ensures I still keep some of that glow. Let your eyes be the judge: what looks good? If you feel as though you’ve stared at a painting for too long, flip it by going to Image>Image rotation>Flip Canvas Horizontal. That way you’ll reboot your brain and can spot mistakes more easily.