Greenish letters

[Picilli]

I don't know is this a bug, or some default setting which interferes
with a display;

Iceacat version 3.0.7-g1

My Firefox runs fine, no problems at all; however, in IceCat many
letters in web pages are partially blueish colored. The same web
pages regular Firefox displays just fine.
Does someone know why letters in IceCat are colored, and how to
remove that problem ?

In both Firefox and IceCat I have FreeSans, FreeMono and FreeSerif.
Anyway, regardless of font chosen letters in web pages displayed by
IceCat are always greenish or blueish. Some letters are purplish
too, "f", "t", "H", "s". Pay attention on "i", small "L", partially
colored "r", "n"...

Here is a screenshot:
http://img208.imageshack.us/img208/4180/blueishletters.png

Please how to correct this ? Thank you very much.