Changing Start lights

Hi,

Does anyone know how to change the start lights on the track. Not the one that appears in the top right hand corner of the screen when you start, but the one that is physically part of the track itself typically attached to a gantry of some kind. I'm playing on some older tracks and I'd like to replace the green/red/green lights to the five red lights. I looked in WAD files for more recent tracks compared to older tracks but could not see an obvious tex file that would need switching replacing.

Thanks.