Cover of Night on Grapest
#494e4f on #880066
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
1.11:1
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 15.0
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#afb5b6 is the nearest colour of the same hue that passes AA on #880066, 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 1.47:1, ΔE00 21.4.
deuteranopia
Ratio 1.02:1, ΔE00 10.1.
tritanopia
Ratio 1.31:1, ΔE00 34.6.
The weakest of the three is deuteranopia, where the two are ΔE00 10.1 apart against 15.0 for a trichromat — still clearly two colours.
Both colours have pages of their own: Cover of Night ·Grapest · the same pair the other way round ·all pairs