Master Chief on Corrosive Green
#507d2a on #54d905
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
2.62:1
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 37.0
Clears Lc 30 — the floor: below this the draft considers text not readable at any size.
Dark text on a lighter ground.
Colour difference
ΔE00 27.5
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#2f5800 is the nearest colour of the same hue that passes AA on #54d905, 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 2.76:1, ΔE00 27.8.
deuteranopia
Ratio 2.55:1, ΔE00 26.3.
tritanopia
Ratio 2.31:1, ΔE00 22.3.
The weakest of the three is tritanopia, where the two are ΔE00 22.3 apart against 27.5 for a trichromat — still clearly two colours.
Both colours have pages of their own: Master Chief ·Corrosive Green · the same pair the other way round ·all pairs