Isn't Rei also, like, "cold"? Blue. Blue cold
Huh yeah, among other things.
JDIC: 冷 【れい】 (n) (1) (abbr) (on floor plans) (See 冷蔵庫) refrigerator; (adj-na,n) (2) (rare) cold; cool; (n) (3) (abbr) (rare) (See 冷酒・れいしゅ) cold sake [Links] (Name entry: 冷 )
'rei' is also 'zero', less relevant here.