By a quirk of etymology, this word in Slovene means not only blue, but also "wise" (in the neuter singular). In Slovene the nasal o of Proto-Slavic evolved into the simple o, whereas in other South Slavic and East Slavic languages, it became u. Hence, "wise" (n.sg.) in SBC is mudro, in Russian, мудро (mudro). Perhaps this is one reason why Slovene and SBC both borrowed the German word blau, reshaping it as plav.