Grapest on Acoustic Brown
#880066 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
1.82:1
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 12.0
Below Lc 15: the draft treats this as not text.
Dark text on a lighter ground.
Colour difference
ΔE00 27.9
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 2.35:1, ΔE00 30.4.
deuteranopia
Ratio 1.63:1, ΔE00 19.4.
tritanopia
Ratio 1.26:1, ΔE00 7.9.
The weakest of the three is tritanopia, where the two are ΔE00 7.9 apart against 27.9 for a trichromat — still two colours, but a closer call than it looks to you.
Both colours have pages of their own: Grapest ·Acoustic Brown · the same pair the other way round ·all pairs