Number / Notch Colour
The photos below show-
All the colours of Backing available.
These will be affected by your choice of using the original OEM bulbs or switching over to newer LEDs.
The difference between using bulbs and white LEDs is that OEM bulbs tend to be incandescent. This incadescence gives out an orangey glow (like an ordinary light bulb). This orange soaks up blue light waves. The effects can be seen below.