Out of the Blue on Cyantific
#1199ee 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
1.60:1
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 18.3
Clears Lc 15 — disabled or purely decorative text, which is not meant to be read.
Dark text on a lighter ground.
Colour difference
ΔE00 27.6
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#004f7f 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 1.57:1, ΔE00 26.7.
deuteranopia
Ratio 1.62:1, ΔE00 23.6.
tritanopia
Ratio 1.75:1, ΔE00 16.5.
The weakest of the three is tritanopia, where the two are ΔE00 16.5 apart against 27.6 for a trichromat — still clearly two colours.
Both colours have pages of their own: Out of the Blue ·Cyantific · the same pair the other way round ·all pairs