Text rendered with the OGL pipeline through the accelerated glyph cache can
sometimes result in pixel values that do not match the expected value. For
example, if you draw red text (ff,00,00) on a white background (ff,ff,ff),
you may end up with off-red pixels (ff,20,20) and surrounding pixels may also
be skewed slightly (ff,fd,fd).

Run the attached testcase and use a pixel magnifier to inspect the color of
the text. The text should be pure-red on a pure-white background.