Hi, at line 80 in the thumbs.as file you will see this:
I think the stuff in the parenthetical is setting the dogear color to the existing thumbnail framecolor.
So delete this stuff in the parenthetical: mXMLManager.thumbnailFrameColor.
Replace it with the hexidecimal value of whatever color you want to use.
For example if you want the dogear to be white then line 80 will look like this:
Most programs that have some kind of color picker will show you the hex number of the color that you pick. Then you can just copy the hex value down for use in simpleviewer.