I'm pretty sure you can use a clear lens and red bulb for rear light/brake light - used to have them on my Land Rover with no issues. They sell kits: Landy Rear Lights

A rear reflector must be red.

"Y mae dafad ddu ym mhob praidd"
1972 4/4, 1981 MGBGT, 1984 FLHT1340, 1980 XLH1000, 1990 ZX10