Comment by boulos

Amy Gooch's Color2Gray and various follow-on work has better coverage of the OP's actual goal:

> evaluate relative brightnesses between art assets, and improve overall game readability

The method in Color2Gray is trying to enhance salience, but the paper does a good job of comparing the problems (including red / blue examples in particular).

Like other commenters, I think oklab would look better than CIELAB on the example given in the OP. https://bottosson.github.io/posts/oklab/#comparison-with-oth... and the Munsell data below it show it to be a lot more uniform than either CIELAB or CIELUV.