I think they mean there many hues that some people will cal blue and other will disagree. And definitely if you try to buy paint and just say you want "blue" there's a huge spectrum of things you might get

This website was doing the rounds not long ago: https://ismy.blue/

Which blue paint? If you are buying by yourself, it might be simple, if you are a decisive sort, but there's more blues than I at least expected.