The color blue is an elusive one - it has a wide range, and interperatations of "blue" differs from person to person!
Blue vs Cyan
This site includes all hues of "blue": the classic RGB blue, as well as cyan, teal, azure, and some indigo.
There's also different concentrations of "blue" - what makes a color "grayish-blue" versus a "cool gray"? I have an idea, but I don't think it's perfect, and again, varies on who you're asking.
Blues that are deemed "gray" are marked with a half moon icon.
What is Indigo anyway?
In my personal opinion, what we percieve as "blue" nowadays is actually indigo!
Colored pencils seem to agree with me on this one.
The "blue" boundary this site tracks are hues 170 - 250.
The key word is "mostly", because there are expections with some named "blue" colors that lean green, or warmer blues (or indigo!) that still looks like blue, but has a hue value of over 240.
Blues that are outside the boundary are marked with a rainbow icon.
Cyan is hue 180. The cyan range is <= 195
Azure is hue 210. The azure range is 196-225
Blue is hue 240 The blue range is >= 226