[UMN_MAPSERVER-USERS] HTTP parameters used to style background color

[Dennis Byrne]

I am using HTTP requests like the following to generate map images.  

http://mydomain.com/fcgi-bin/mapserv?img.y=200.0&img.x=300.0&imgext=-2126099.0%20174206.0%201534483.0%202614595.0&zoom=1&layers=alaska_gen&layers=arimspt&map=%2Fopt%2Fmaps%2Falaska_test.map&

The background for these images defaults to grey.  Can anyone tell me how to change this color ... a link to this in the documenation would be appreciated as well.

Dennis Byrne