Comment # 10 on bug 1172022 from Andrei Borzenkov

(In reply to Bruno Pesavento from comment #9)
> Looks like I had the "Subpixel" antialiasing checked; reverting to "Standard
> (Grayscale)" makes the disturbing colored fringes disappear.

Fixed for me on Xfce too. Setting is called "Sub-pixel order" and selecting
"None" returns fonts to 2.9 look. Default was RGB.

It is still serious regression. Users are not expected to be forced to
reconfigure obscure parameters on what is simple maintenance update.