zlacker

Green has higher luminance than blue at equivalent saturation. The values for SMS and iMessage background colors are, respectively and in sRGB, #00CC46 and #0080FF, corresponding to relative luminance values of 0.436 and 0.227 according to the WCAG 2 formula.

With white foreground text, this gives a contrast ratio of 2.15:1 for SMS and 3.79:1 for iMessage. WCAG 2.x AA level compliances requires a contrast ratio of at least 4.5:1 for normal text and at least 3:1 for large text.

https://www.w3.org/WAI/WCAG21/Understanding/contrast-minimum...

>>AprilA+(OP)
Thanks! If you have a calculations workflow already, what would the contrast ratios (even if approximate) be for old iOS? To a human eye it truly looks like SMS got way worse whereas iMessage stayed around the same.

>>madars+T
The pre-iOS 7 graphics have black text over a non-uniform background color as compared to white text over a uniform background color. This gives us ranges instead of a single value, but even in the worst case, black is a vastly more legible foreground color:

           | iOS 5-6     | iOS 7+ |
  ---------+-------------+--------+
  SMS      | 11.3 - 13.4 | 2.2    |
  iMessage | 11.8 - 14.1 | 3.8    |

>>AprilA+(OP)
Thank you. FWIW, here is it under iOS 16 with Accessibility > Display & Text Size > Increase Contrast turned on.

https://imgur.com/a/b61lmAf

To my eyes, the green/blue doesn't make much difference in terms of legibility. I obviously find the reduced contrast throughout iOS annoying and keep increase contrast turned on.