Diesel on Ethereal Espresso
#322c2b on #3e2723
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
1.01:1
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 8.9
clearly different
Between 5 and 10 — nobody would call these the same colour.
What the text colour has to become
#999190 is the nearest colour of the same hue that passes AA on #3e2723, 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 1.04:1, ΔE00 3.5.
deuteranopia
Ratio 1.01:1, ΔE00 5.4.
tritanopia
Ratio 1.06:1, ΔE00 3.9.
The weakest of the three is protanopia, where the two are ΔE00 3.5 apart against 8.9 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: Diesel ·Ethereal Espresso · the same pair the other way round ·all pairs