@Gerard: I too, experienced those funny colors, which makes SA look like a damned disco, I still remember those funny greens and pinks and blues and all that flashing...
And really speaking, when I flew the Hydra from the Airstrip towards the Gant Bridge and surrounding areas, I too had the same problem....I tried re-installing the game, I did it twice...then it worked properly.
Despite this, I'll suggest if you have any mods installed, first get rid of them
[usual way to get off the mods = re-install].
Hope this helps.