I appear to have the same problem (inverted colours) on an early 2005 G5 iBook running Gentoo with anything more recent than linxu-3.7.0 with UMS. KMS definitely seems to be linked to the problem. FVWM, xterm and ImageMagick's display seem affected; maybe Geeqie too. Firefox and Gnome Terminal get their colours right, though. Everything seems usable otherwise.
Linux gloduk 3.10.7-gentoo #9 PREEMPT Fri Sep 6 21:31:50 EST 2013 ppc 7447A, altivec supported PowerBook6,5 GNU/Linux
I appear to have the same problem (inverted colours) on an early 2005 G5 iBook running Gentoo with anything more recent than linxu-3.7.0 with UMS. KMS definitely seems to be linked to the problem. FVWM, xterm and ImageMagick's display seem affected; maybe Geeqie too. Firefox and Gnome Terminal get their colours right, though. Everything seems usable otherwise.
Linux gloduk 3.10.7-gentoo #9 PREEMPT Fri Sep 6 21:31:50 EST 2013 ppc 7447A, altivec supported PowerBook6,5 GNU/Linux
x11-drivers/ xf86-video- ati-6.14. 6-r1