I'm colorblind, but I ended up getting a 0.0028 "much better than average" score. Hmm... Fun site!

To promote some further reading:

OKLab isn't actually a perceptually uniform colorspace. It's better than others, but it was specifically chosen as a tradeoff between accuracy and speed (hence the name OK). When you start digging this deep, you quickly learn that we have yet to invent any perceptually uniform colorspaces; even the most precise models we have end up using fits and approximations. Color has some really inconvenient properties like depending strongly on brightness and background. Frankly, given the differences in human biology (having orders of magnitude differences in relative numbers of each cone, for instance), it's surprising we agree as much as we do! Human color perception is an endless pit of complexity.

(Note, I don't say any of this to detract from what you've built here, merely expand. Your site is awesome and I love it!)