The relevant part of the stylesheet page in question, stvb3r.css, is here:
::selection {
/*
background-color: #e0f2c2;
color: #4da400;
*/
}
It originally changed the selected text on an SDMB webpage to green-on-bright-green (which I vaguely remember seeing a while ago). The selection of the color was commented out, however, leaving blank “instructions” for the browser. Most browsers seem to think that should mean to leave the selection color alone, but Chrome seems to get confused.
Moving the commenting characters to outside the ::selection element – something like
/*
::selection {
background-color: #e0f2c2;
color: #4da400;
}
*/
seems to fix the problem on Chrome. I can’t test that easily on other browsers, though.