Acoustic Brown on Matt Green
#766b69 on #39ad48
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
1.78:1
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 18.6
Clears Lc 15 — disabled or purely decorative text, which is not meant to be read.
Dark text on a lighter ground.
Colour difference
ΔE00 36.0
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#382f2d is the nearest colour of the same hue that passes AA on #39ad48, at 4.50:1. Only the lightness moved — which is the point: your colour stays recognisably your colour.
And to someone missing a cone
protanopia
Ratio 2.01:1, ΔE00 29.1.
deuteranopia
Ratio 1.65:1, ΔE00 23.3.
tritanopia
Ratio 1.65:1, ΔE00 55.3.
The weakest of the three is deuteranopia, where the two are ΔE00 23.3 apart against 36.0 for a trichromat — still clearly two colours.
Both colours have pages of their own: Acoustic Brown ·Matt Green · the same pair the other way round ·all pairs