Same issue. The overall RGB effect of this board is absolute rubbish.
Either the RGB LED's are too weak, or the cover is too thick to allow for enough light to break through.
If you have ANY other light source in your PC, the effect of the RGB is diminished severely.
In my case, I have some Corsair LL fans, G.skill memory and a Corsair H150 all with RGB. It overpowers the motherboard lighting effects to the extent where it's barely visible.
If my build didn't take so long to dismantle and rebuild it would have been RMA'd ages ago.
Pics below for context...