I'm currently blocking out a level inside UE4 and i went to test a potential design for a wall decal. The Decal is set to deferred decal and is using the same colour orange as whats on the wall but its really faint/watered down looking. When i move the decal outside the level and place it on the wall the colour is…
You could always try multiplying the base color on it self. You might have to play with it a little to get the right saturation but it should at least be closer.