Cerulean Blue:

Cerulean stems from the Latin word “caeruleus” which means heaven or sky. Cerulean is a true blue color between azure, teal, and sky blue.

a : a variable color averaging a strong greenish blue that is bluer and duller than grotto or cobalt blue and bluer and lighter than indigo carmine.

b : a strong blue that is greener and stronger than Sèvres and greener, lighter, and stronger than Victoria blue.

I don't think it's the color of the U.N. Helmets, which are more of a light blue.