Atlas Cedar on Cyantific
#5ca0a7 on #77c9c2
Body text at this size
And the smaller size most interfaces actually use for paragraphs — the size that decides whether a pair is usable.
Caption text, which almost nothing passes.
WCAG 2.1
1.55:1
Fails AA
Not AAA (7:1). Swapping the two colours gives the same number — the ratio does not know which is the text.
APCA
Lc 17.5
Clears Lc 15 — disabled or purely decorative text, which is not meant to be read.
Dark text on a lighter ground.
Colour difference
ΔE00 12.5
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#00545b is the nearest colour of the same hue that passes AA on #77c9c2, at 4.50:1. Only the lightness moved, and some chroma was given up to stay inside sRGB — which is the point: your colour stays recognisably your colour.
And to someone missing a cone
protanopia
Ratio 1.56:1, ΔE00 12.7.
deuteranopia
Ratio 1.55:1, ΔE00 11.8.
tritanopia
Ratio 1.43:1, ΔE00 10.5.
The weakest of the three is tritanopia, where the two are ΔE00 10.5 apart against 12.5 for a trichromat — still clearly two colours.
Both colours have pages of their own: Atlas Cedar ·Cyantific · the same pair the other way round ·all pairs