For me, it's all about being unique.
Sky-white-navy, as you say, is totally unique. sky-white-sky/sky-sky-sky/sky-sky-white could be anyone from Coventry to Lazio to Cetla to Zenit.
Even if you deleted all the text from this poster, it just looks like Manchester City:
We had navy socks from our inception in 1894 right through to 1951 (with the exception of two years with black socks) it's a shame we never have them as part of our kits these days, i think it looks great. Instantly recognisable as City.