For best results, the LED color should be the same as the lens color. If the bulb is behind a clear lens, use the appropriate color for turn and brake light functions.
When installed in a housing that has a matching colored lens, red and amber bulbs will appear brighter than white LED bulbs—even though they have lower lumen outputs.
As an example: a red lens will filter out all but the red portion of light from a bulb, so if the light being emitted from the bulb is all red, none or very little light will be blocked by the lens. The light from a white LED bulb contains very little light in the red portion of the visible spectrum, so most of the light that contributes to its higher lumen value would be filtered out by a red lens. This makes the white bulb appear dimmer than the red bulb.