According the Road Vehicles Lighting Act, there are two choices of colour that comply with regulations in the UK and they are white or yellow (not amber).

www.legislation.gov.uk

See:

Schedule 4, part 1, section 7

REQUIREMENTS RELATING TO OBLIGATORY DIPPED-BEAM HEADLAMPS

Schedule 5, part 1, section 7

REQUIREMENTS RELATING TO OBLIGATORY MAIN-BEAM HEADLAMPS

So, if you want coloured headlamp covers, then yellow is your only "legal" option.

__________________