Either orange or with special coating.
The special coated bulb only lights orange when you use the indicator (bulb is usually used with transparent lenses).
Single
Bulb 12V 60/55W P43T T16X75 C-8/C-8 H4 UVS HD HIGHLIFE, H4...
Repair plug for indicators / licence plate illumination...
Rubber seal for front indicator lens
For BMW K100RS,...