Perhaps it's using one of those luminance-from-RGB vectors somewhere in the calculation? That could overrate the contribution of green to the appearance.

Nope - it's a dull blue, with a _hint_ of green.

FWIW, I don't know if I'm a tetrachromat or not, but I do have a very good colour detecting ability.

Do all 16 million color combinations have names? That would be crazy!