Like how the color Pink is often associated to females, the color Blue is frequently linked to males. Thus, it's not at all surprising to see this paint color in Tanki X, a game that's played mainly by males.
The Blue paint itself isn't exactly useful as a camouflage paint on its own, in a way that's similar to the Orange paint. Unlike the Orange paint though, the Blue paint doesn't exactly scream out "Fight me!" to your opponent.
However, as some players may point out, despite being mainly aesthetic in nature, the blue paint can be pretty helpful when battling other tanks in a map with a darker environment, such as the newly released West prime.