Olympian Blue on Pastel Brown
#1c4c8c 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
1.67:1
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 11.8
Below Lc 15: the draft treats this as not text.
Dark text on a lighter ground.
Colour difference
ΔE00 36.1
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#e8f1ff is the nearest colour of the same hue that passes AA on #836953, at 4.50:1. Only the lightness moved, and some chroma was given up to stay inside sRGB — which is the point: your colour stays recognisably your colour.
And to someone missing a cone
protanopia
Ratio 1.51:1, ΔE00 38.2.
deuteranopia
Ratio 1.76:1, ΔE00 42.8.
tritanopia
Ratio 1.81:1, ΔE00 65.5.
The weakest of the three is protanopia, where the two are ΔE00 38.2 apart against 36.1 for a trichromat — still clearly two colours.
Both colours have pages of their own: Olympian Blue ·Pastel Brown · the same pair the other way round ·all pairs