Its a bug. There is an ocassional red cloud only in Poor or Inclement weather but its pretty infrequent.
The devs have looked into it but again its infrequent and would take a lot of trial and error to try and totally eliminate it. In the BDG.txt file are a bunch of sky and cloud paramters such as:
Weather_CloudAlbedo = 1.000000
Weather_SunGlow = 0.250000
Weather_SunFlare = 0.500000
Weather_SkyLambda3 = 2250000.000000
Weather_SkyLambda2 = 1604038.000000
Weather_SkyLambda1 = 1250000.000000
Weather_SunLambda3 = 0.506000
Weather_SunLambda2 = 0.560000
Weather_SunLambda1 = 0.685000
Weather_SkyExposure = -0.350000
Weather_Turbidity = 1.800000
Weather_SkyGamma = 3.000000
Weather_SunIntensity = 150.000000
Weather_MieG = -1.500000
Weather_MMult = 0.000001
Weather_RMult = 0.018000
Weather_SunColor = 1.000000
These are all interrelated - a change in one affects the others. Tweaking might "fix" it but then cause other anomalies. It is possible to play around with them safely - just make a backup of the BDG.txt file so you can restore these lines if needed (one can even delete the file entirely and it will be regenerated at default values next time Bob2 is run). Unfortunately the various paramteters are not fully documented but there is a little info here:
http://shockwaveproductions.com/foru...pic.php?t=5099