Endless Galaxy on Purple Climax
#000044 on #8800ff
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
3.22:1
Large text only
Not AAA (7:1). Swapping the two colours gives the same number — the ratio does not know which is the text.
APCA
Lc 25.4
Clears Lc 15 — disabled or purely decorative text, which is not meant to be read.
Dark text on a lighter ground.
Colour difference
ΔE00 30.8
different colours
Above 10 — related only in the sense that both are colours.
What the text colour has to become
#cfdfff is the nearest colour of the same hue that passes AA on #8800ff, 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 2.73:1, ΔE00 26.4.
deuteranopia
Ratio 3.48:1, ΔE00 30.8.
tritanopia
Ratio 3.35:1, ΔE00 29.1.
The weakest of the three is protanopia, where the two are ΔE00 26.4 apart against 30.8 for a trichromat — still clearly two colours.
Both colours have pages of their own: Endless Galaxy ·Purple Climax · the same pair the other way round ·all pairs