Can we get more information Ed Kelly? Like what manufacturer is the loco made by? Is this decoder install being done by you?, etc?
Somewhat agreeing with Bruk. Generally, any LED will need to have dropping resistors wired in line with the lighting function outputs of the decoder. If you don't do this, the LEDs will light once, but only for a very brief moment. After that, they are burned out. I have seen diesel locos from Atlas O (2-Rail) where the headlight and backup light were 1.5 volt light bulbs and the marker/class lights were red colored LEDs. The only way to know for sure is to remove the shell and verify. I'm not understanding the different colors you are reporting. You may have bi-colored LEDs. I'm not entirely sure how these bi-color LEDs work--the color change may be done through polarity switching.
Let us know what you find out.
Kindest Regards,
Brian Huang
