According to Colorado law, the markers MUST be of the color intended. Forward of the vehicle's centerline (Looking at the side, showing to the side) must show amber, aft of the centerline must be red. You could use clear lenses as long as the underlying bulb is of the appropriate color. There is no law stating the actual lens color, just that the light emitting from said lamp is the correct color. I'm sure most other states are in the same mind.

I loved to use the white (clear) colored bulb under a clear turn signal lens for probable cause for a traffic stop..


One thing that did get grandfathered in was the dual faced fender lights you see on large trucks. They have to have the amber side faceing forward and the red facing aft.

Does that help?