Diesel on Pastel Brown
#322c2b on #836953
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
2.69:1
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 23.1
Clears Lc 15 — disabled or purely decorative text, which is not meant to be read.
Dark text on a lighter ground.
Colour difference
ΔE00 25.0
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#f7efed is the nearest colour of the same hue that passes AA on #836953, 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 2.59:1, ΔE00 23.6.
deuteranopia
Ratio 2.74:1, ΔE00 25.4.
tritanopia
Ratio 2.87:1, ΔE00 26.9.
The weakest of the three is protanopia, where the two are ΔE00 23.6 apart against 25.0 for a trichromat — still clearly two colours.
Both colours have pages of their own: Diesel ·Pastel Brown · the same pair the other way round ·all pairs