Castro on Olympian Blue
#44232f on #1c4c8c
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
1.61:1
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 9.1
Below Lc 15: the draft treats this as not text.
Dark text on a lighter ground.
Colour difference
ΔE00 30.4
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#dcb1bf is the nearest colour of the same hue that passes AA on #1c4c8c, 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 1.80:1, ΔE00 21.6.
deuteranopia
Ratio 1.52:1, ΔE00 25.5.
tritanopia
Ratio 1.44:1, ΔE00 54.5.
The weakest of the three is protanopia, where the two are ΔE00 21.6 apart against 30.4 for a trichromat — still clearly two colours.
Both colours have pages of their own: Castro ·Olympian Blue · the same pair the other way round ·all pairs