Alas, it seems like WebGL is completely broken in Firefox 23.0, all I get is
"It doesn't appear your computer can support WebGL. Click here for more information."
With Seamonkey 2.17.1 though my testpage
http://mc.pp.se/webgl/webgltest.html
seems to work correctly (cube is yellow). So maybe the actual colour bug was fixed in Firefox too, although I can't verify due to the other issue...
Alas, it seems like WebGL is completely broken in Firefox 23.0, all I get is
"It doesn't appear your computer can support WebGL.
Click here for more information."
With Seamonkey 2.17.1 though my testpage
http:// mc.pp.se/ webgl/webgltest .html
seems to work correctly (cube is yellow). So maybe the actual colour bug was fixed in Firefox too, although I can't verify due to the other issue...