Master Chief on Castro
#507d2a on #44232f
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
2.82:1
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 -23.4
Clears Lc 15 — disabled or purely decorative text, which is not meant to be read.
Light text on a darker ground — the negative sign is the polarity.
Colour difference
ΔE00 48.5
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#71a04e is the nearest colour of the same hue that passes AA on #44232f, 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 3.18:1, ΔE00 38.5.
deuteranopia
Ratio 2.65:1, ΔE00 29.8.
tritanopia
Ratio 2.51:1, ΔE00 48.3.
The weakest of the three is deuteranopia, where the two are ΔE00 29.8 apart against 48.5 for a trichromat — still clearly two colours.
Both colours have pages of their own: Master Chief ·Castro · the same pair the other way round ·all pairs