How to add more colors to decals

I want my decals to match the walls and doors of my hospital, but the walls and doors all have up to 10 colors and the decals have only 5. I tried adding more colors to the decals in ColorSets.xml and Decals.xml but it doesn't work. What do i have to change to have all 10 colors in the decals?


All the walls have 10 colors


But the decals all have only 5!