Abyssal Waters on Black Sabbath
#005765 on #220022
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
2.34:1
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 -13.5
Below Lc 15: the draft treats this as not text.
Light text on a darker ground — the negative sign is the polarity.
Colour difference
ΔE00 40.9
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#3e8493 is the nearest colour of the same hue that passes AA on #220022, 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 2.61:1, ΔE00 22.9.
deuteranopia
Ratio 2.20:1, ΔE00 18.8.
tritanopia
Ratio 2.18:1, ΔE00 43.1.
The weakest of the three is deuteranopia, where the two are ΔE00 18.8 apart against 40.9 for a trichromat — still clearly two colours.
Both colours have pages of their own: Abyssal Waters ·Black Sabbath · the same pair the other way round ·all pairs