Endless Galaxy on Quiet Abyss
#000044 on #160435
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
1.02:1
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 6.7
clearly different
Between 5 and 10 — nobody would call these the same colour.
What the text colour has to become
#577ac4 is the nearest colour of the same hue that passes AA on #160435, 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 1.00:1, ΔE00 4.4.
deuteranopia
Ratio 1.03:1, ΔE00 5.2.
tritanopia
Ratio 1.02:1, ΔE00 12.8.
The weakest of the three is protanopia, where the two are ΔE00 4.4 apart against 6.7 for a trichromat — effectively one colour. If anything on your interface depends on telling these apart, it needs a second signal.
Both colours have pages of their own: Endless Galaxy ·Quiet Abyss · the same pair the other way round ·all pairs