Created attachment 127816 [details]
WebGL coloring glitch.

Running some OpenGL programs on PowerMac G5 with NVIDIA GeForce 6600LE shows
problematic rendering:

- Wrong coloring, simply looks like inverts or blue/purple hue (WebGL demo,
Plasma Discover, Compiz, Linthesia, etc.)
- Text disappears (in the case of Plasma Discover).
- Flickering and glitchy flashing texture in general (in the case of
Linthesia).

This problem could be reproduced with Mesa 12.0.3 and 13.0.0 (which relates
with another issue I have just reported in this section
https://bugs.freedesktop.org/show_bug.cgi?id=98629).

Any how, some screenshots are provided below to demonstrate my issue.