I have noticed 'blended' colors are pretty far from accurate...ie a true 'snow white' on my nodes is about 255, 208, 107 in RGB, a nice orange 135, 19, 00, nice yellow 83, 29, 00 etc. With that being said, the flag should mostly represent primary colors...red, blue - the only reason for green to be on would be for the white blend.
Out of curiosity, does the green seem to completely replace one color (ie blue or white) or does it just seem to be randomly mixed around the pattern? Also it it incorrect on all strings, or does it start at a certain point?