Black Box on Galactic Federation
#0f282f on #330077
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
1.03:1
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 0.0
Below Lc 15: the draft treats this as not text.
Too close to call.
Colour difference
ΔE00 15.7
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#76929a is the nearest colour of the same hue that passes AA on #330077, 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 1.05:1, ΔE00 21.5.
deuteranopia
Ratio 1.07:1, ΔE00 18.6.
tritanopia
Ratio 1.05:1, ΔE00 1.3.
The weakest of the three is tritanopia, where the two are ΔE00 1.3 apart against 15.7 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: Black Box ·Galactic Federation · the same pair the other way round ·all pairs