The funny thing about blue in Japanese is that it’s a fairly new concept.
It wasn’t until the Heian period (794-1185) that a separate word for green ‘midori’ started being used.
But ‘midori’ was still considered just a shade of blue
It was only after World War II that the distinction was fully implemented into the language.
That’s why you’ll hear people say “The traffic light has turned blue” or “Blue apple”…