Master Chief on Dragon’s Fire
#507d2a on #fc4a14
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
1.42:1
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 11.3
Below Lc 15: the draft treats this as not text.
Dark text on a lighter ground.
Colour difference
ΔE00 55.1
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#142a00 is the nearest colour of the same hue that passes AA on #fc4a14, 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 1.10:1, ΔE00 2.8.
deuteranopia
Ratio 1.73:1, ΔE00 17.2.
tritanopia
Ratio 2.49:1, ΔE00 61.8.
The weakest of the three is protanopia, where the two are ΔE00 2.8 apart against 55.1 for a trichromat — effectively one colour. If anything on your interface depends on telling these apart, it needs a second signal.
Both colours have pages of their own: Master Chief ·Dragon’s Fire · the same pair the other way round ·all pairs