When traveling through caves I would occasionally see the space a short distance from me turn solid green or blue ( looked like 0, 255, 0 or 0, 0, 255 ) for less than a second, then turned solid black ( 0, 0, 0 ) and stayed that way. The "black wall" looked spherical, and moved with me. It would eventually disappear. I can't make it happen intentionally, but I did see it twice in under 30 minutes. I have attached a screenshot and my options.txt.

I have not tested this under different conditions, I only get about 12FPS on this laptop so I have a difficult time playing the game at all.

I also get empty triangles popping up on the surface of water, but those are too fast to get a screenshot of, might be unrelated, those have happened since 1.5.

When asked to force a crash I saw the black fog about a minute after loading the game. While forcing the crash with F3 + C, the fog dissipated, did not simply disappear, it actually took time and faded away over a couple seconds. I have attached the crash report.