Here's some movies showing various light effects.  You will need Apple's Quicktime to view them.  Get it here.

Digitrax DH-163IP ditch lights, using white LEDs.

TCS TH-141 Ver 9 ditch lights, using white LEDs.

WP F3A with NCE D13SRJ and 5mm sunny white LED for both the headlight (with dimming) and Mars light. (4.4 meg)

CB&Q F3A with NCE D123SRJ and 5mm golden glow white LED for the headlight and a white 1.8mm (with filter to fix the blue tint) and red 1.8mm LED next to each other for the Mars light.  (4.4 meg)  See a inside pic here.