yeah, I tried it in FF and it replaced the blue gradient png and the blue bgcolour (on the sides) that are imposed by the blue stylesheet.  there are sevl. more blues ya can kill on that, however the other two sheets (site.css and main.css) don't appear to have any blues in 'em.  the one where ya kill the gold threadnames is the main.css IIRC.  here is how to do it: ya don't actually try to replace their sheets, but just copy the offending lines with blue or gold colours, paste 'em in yer sheet, edit to white/grey/black e.g., then yer sheet should supercede the same lines in theirs.