A pair of headlights must emit light of substantially the same colour and intensity, emit a steady colour of either white or yellow and be visible from a reasonable distance.
At least 50% of the reflecting surface must be visible from a reasonable distance.
All indicator must emit amber light. At least 50% of the lamp must be visible. Light must be visible from a reasonable distance.
No law on fog lights as they are an additional extra and not M.O.T bound.
A headlamp or rear tail lamp altered in this way is not a reason for MOT rejection. So long as light outputs are not adversely reduced, it emits the appropriate correct colour and the mask is securely attached.