Opera on Acoustic Brown
#816575 on #766b69
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
1.01:1
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 0.0
Below Lc 15: the draft treats this as not text.
Too close to call.
Colour difference
ΔE00 10.5
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#ffeaf6 is the nearest colour of the same hue that passes AA on #766b69, 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 1.04:1, ΔE00 8.7.
deuteranopia
Ratio 1.01:1, ΔE00 6.8.
tritanopia
Ratio 1.03:1, ΔE00 7.2.
The weakest of the three is deuteranopia, where the two are ΔE00 6.8 apart against 10.5 for a trichromat — still two colours, but a closer call than it looks to you.
Both colours have pages of their own: Opera ·Acoustic Brown · the same pair the other way round ·all pairs