I'm working on a car signage concept in Photoshop. To achieve (reasonable) realism with the white sticker I simply knocked back the opacity a little. I think it gives the illusion of white but with the shadows and highlights of the car contours evident.
However, the bottom panel has a blue/cyan background. This too should be affected by the shadows and highlights. Below you can see how terrible it looks without showing the underlying contouring.
I had (arrogantly) assumed this would be solved with one of the layer blend modes, probably "hue". After fifteen years I still don't know what they do of the top of my head and I generally click through them until one works! To my amazement, none will accomplish this. Probably because the hue is so much lighter, I really don't know.
In fact the "hue" blend mode does (somewhat) realistically change the colour, but to a deep purple, not the intended cyan. "Screen" with lowered opacity isn't bad...but I am sure there is a simple way!
How would you go about realistically changing the colour of that lower panel to blue/cyan, whilst maintaining the shadows and highlights?