Magami No ER: I've actually seen skies at dusk turn a beautiful red color, dying everything in a wonderful rouge. Pretty, indeed
Mr. Tines: "Red sky… Red, the colour I hate." If a blue sky with clouds is symbolic elsewhere, is this, too? Or is it a case of "sometimes a cigar is just a cigar"?
Reichu: Color symbolism is sort of like numerology in its almost futile ambiguity. As will be proven by Rei's monologue later on, though, the color red certainly is significant in some way… Perhaps red represents imprisonment and containment, whereas blue is openness and freedom? I'm really just pulling that out of my arse, though.
OMF: It's got to represent blood, violence, anger, etc. Negative emotions. Especially considering Rei's words following the above quote by Mr. Tines.
Reichu: I dunno, man. That seems a bit too obvious. Especially since you guys are getting Rei's mind-boggling psychology involved.