Hacker News Reader

The funny thing is that simply changing the text color to black causes the green-on-black to pass all those metrics, with the blue-on-black passing everything but WCAG AAA with the normal font (but still passes on the larger font).

(Same result using #64C567 for the green bubbles, which a sibling pointed out is the correct value.)

Wrong color, iMessage uses #64C567 for the green background, which has a higher contrast than the pair you supplied (1.85 versus 2.15)

Still doesn't pass? Also thanks for pointing out the error!

I'm confused by all the mention of "what colour apple uses" in messages, message bubbles are a mask over a gradient

There is an "Increase Contrast" option in Settings for visually-impaired users.