I am particularly interested in the phrase 「水{みず}色{いろ}時{じ}代{だい}」. Did it come from the old manga that used the phrase as its title, or has the phrase been carrying that particular cultural connotation long before the manga?

So how and when did the term 水色 start to be associated with youth, adolescence and puberty? 

p/s: While on the same topic, I'd like to share this interesting chart on how different cultures interpret different colors: <http://www.globalization-group.com/edge/resources/color-meanings-by-culture/>