Opera on Belladonna
#816575 on #220011
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
3.77:1
Large text only
Not AAA (7:1). Swapping the two colours gives the same number — the ratio does not know which is the text.
APCA
Lc -25.5
Clears Lc 15 — disabled or purely decorative text, which is not meant to be read.
Light text on a darker ground — the negative sign is the polarity.
Colour difference
ΔE00 31.1
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#8e7182 is the nearest colour of the same hue that passes AA on #220011, 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 3.70:1, ΔE00 30.7.
deuteranopia
Ratio 3.80:1, ΔE00 31.2.
tritanopia
Ratio 3.69:1, ΔE00 35.2.
The weakest of the three is protanopia, where the two are ΔE00 30.7 apart against 31.1 for a trichromat — still clearly two colours.
Both colours have pages of their own: Opera ·Belladonna · the same pair the other way round ·all pairs