well, arguably, navy versus cornflower would handily cover pedantic differentiation, as needed.
put another way, one can easily counter that the flag and the sky handily share similar saturation of the same hue, differentiated only by the value of darkness.
take it one step further, and the sky at dusk will drop its brightness, and even if only for a moment, match the flag’s deeper blue, until the sun completely sets and the night sky becomes black, when not contaminated by light pollution.
It does (also turquoise and others), however I found that unless someone worked with color, or visual media, painting, graphic design etc. they won't use those names in colloquial speech.
"Did you see that cyan car that drove by?" is not something the majority of people in US might say while in Russia they will use the adjective goluboy and would say it is a completely different color from dark blue.
Printers needed a technical term for this color which they wanted to distinguish from common blue pigments used in painting so they pulled the Greek word for blue.
It shouldn’t be used to refer to a broader color category, and definitely should not be used to refer to blue–green colors. For that stick to blue–green, greenish blue, or teal.
Similarly magenta is a colorful moderately purplish red color, again of medium lightness (named for a famously bloody battle). Again printers adopted this as a technical term because it is a bit different than the “red” pigments commonly used in painting.
The names “cyan” and “magenta” really should not be used to refer to additive mixtures like sRGB #00FFFF or #FF00FF. These colors are unrecognizably far away from printing ink colors.
