Grapest on Opera
#880066 on #816575
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
1.81:1
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 11.8
Below Lc 15: the draft treats this as not text.
Dark text on a lighter ground.
Colour difference
ΔE00 21.6
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#ffe9f5 is the nearest colour of the same hue that passes AA on #816575, 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 2.26:1, ΔE00 23.5.
deuteranopia
Ratio 1.65:1, ΔE00 14.5.
tritanopia
Ratio 1.30:1, ΔE00 6.9.
The weakest of the three is tritanopia, where the two are ΔE00 6.9 apart against 21.6 for a trichromat — still two colours, but a closer call than it looks to you.
Both colours have pages of their own: Grapest ·Opera · the same pair the other way round ·all pairs