If you google color codes there are a lot of websites that will let you pick a color and the site tells you how much red, green and blue make it up. For example:
https://htmlcolorcodes.com/
As you move from blue to yellow you decrease the amount of blue but you have to be pretty far toward yellow before you don't have any blue, and even that's only true if the colors are very saturated.
If a manufacturer makes a reader with a green light option he's going to need a different way to market it.
Barry