How to preserve rainbow Poplar colors?

[bradleyheathhays]

Title says it all.

One...is there any way to preserve the colors of rainbow poplar?

and

Two...how faded does rainbow poplar get when it's exposed to the sun?

 

[2feathers Creative Making]

This is aged rainbow poplar. I have been unable to retain any green or blue coloration. Ever. All shades of brown from beige to dark chocolate. This is a wall in our bathroom. Gets very little uv exposure. Has a polyurethane coating so it isn't getting much oxygen either. I wonder, but have never seen the research to tell, if stabilizing with cactus juice would stop or slow the color fade like it seems to with flame box elder.