I've encountered gases changing color before in a weird way (carbon dioxide having bluish and reddish shadows instead of pure greyish) but I thought it was my old pc or the 3x speed causing it but there was no performance issues or 3x speed this time. Pausing the game reverts colors to their correct hue
Colors revert to normal when you pause:
Open save file. Look around the map for a while (~1min). Colors start to seem wrong...