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 Instrument Lighting
12V/1,2W W2x4,6d, T5x20mm...
These LED front indicators are available as a set for the...
Bulb 12V 60/55W P43T T16X75 C-8/C-8 H4 UVS HD HIGHLIFE, H4...