I "discovered" little trick: You must replace your desktop standby picture with SWF-file.
You needs to create new file in macromedia flash mx 7.2 or higher with size 240x320.
Then insert there your background picture, click on Actions and instert next ActionScript:
fscommand("illumination", "rgbon?ledid=1&R=0&G=100&B=0;rgbon?ledid=2&R=0&G=100&B=0;setGlobalRGBValue?R=0&G=100&B=0;");
Highlighted numbers you may change to create your color.
Then Export with option Flash Light 1.1 into SWF file.
Also you may insert this swf in your THEME by correcting string for example:
<Standby_image Source="BackgroundGreen+-AF8-SEMC+-AF8-Filtered.swf" />
Be shure - color will go back forever : )
You may download corrected default theme Clarity for testing, where color _always go back_:
Dump.Ru Theme
And source FLA:
Dump.Ru FLA
Also DEMO swf:
Dump.Ru DEMO