I use GK Highighter quite a bit. I am working on a new site using iLife. I put GK Highighter in the banner position.
The text that is displayed is surrounded by a green highlight that covers any background color I put in the module.
I tried modifying the colors in template > gk_stuff with no luck. I've also tried in the module files without success.
Assuming I don't fix it before you read this the link is
http://www.dovetrader.com/demo-MKHSHockey/
Thanks.