#A855F7 on white
Tailwind purple-500 — roughly Amethyst — measured against white to WCAG 2.2 and APCA.
3.96:1
contrast ratio · APCA Lc 64
The quick brown fox
…and the same at 13 px
…and the same at 13 px
✕ Body text (AA, 4.5:1)
✕ Body text (AAA, 7:1)
✓ Large text (AA, 3:1)
✓ Borders and icons (1.4.11, 3:1)
The nearest colour that passes
Keeping the hue and moving only the lightness, #953FE1 is the closest shade to #A855F7 that clears 4.5:1 on white — at 5.15:1.
#A855F73.96:1 — fails
#953FE15.15:1 — passes
Under colour blindness
Contrast is a lightness relationship, so a ratio survives colour blindness — but the pair can still lose the distinction it was carrying. This is the same two colours as seen with each dichromacy.
| Vision | Foreground | Background | Ratio |
|---|---|---|---|
| Normal | #A855F7 |
#FFFFFF |
3.96:1 |
| Protanopia red-blind, ~1% of men |
#8C8BDE |
#FFFFFF |
3.06:1 |
| Deuteranopia green-blind, ~6% of men |
#9095D7 |
#FFFFFF |
2.81:1 |
| Tritanopia blue-blind, rare |
#A5C6C1 |
#FFFFFF |
1.83:1 |
What the thresholds mean
- 4.5:1 — WCAG 2.2 success criterion 1.4.3, the minimum for body text.
- 3:1 — the minimum for large text (18.66 px bold or 24 px regular) and, under 1.4.11, for any non-text thing you have to perceive: input borders, icons, focus indicators.
- 7:1 — AAA, criterion 1.4.6.
- APCA Lc 64 — a perceptual model that accounts for polarity, so dark-on-light and light-on-dark are not treated as the same problem. It is the direction WCAG 3 is heading and it disagrees with the ratio often enough to be worth reading alongside it.
Related
Fixing one pair is not the job
ColorsMine checks every pairing a palette implies, in light and dark, and names the single change that moves the grade most.
Open ColorsMine