Create a free text annotation (type 3) using AddAnnotEditBox
The colour sets OK but cannot be read back using GetFillColor() which always returns zero. Instead it can be read using using GetStrokeColor().
This seems to be a bug, as the text appears filled, not stroked.
Also, setting the colour of a free text annotation does not seem to work. The first time you try (using SetFillColor or SetStrokColor) nothing happens. The second time you try, the annotation vanishes.