All WCAG criteria
WCAG 2.1·Perceivable·1.4 Distinguishable

1.4.1 Use of Color

Level A

Color must not be the only way to convey meaning — always pair with text, icons, or patterns.

Why it matters

About 8% of men have some form of colorblindness; red/green status indicators alone exclude them.

Common failure
<span style="color:red">Required</span>
Accessible version
<span style="color:red">Required *</span>

How OnlyEnable handles this

Partially mitigated. OnlyEnable's "Highlight Links" profile underlines all links to add a non-color indicator.

Related criteria in 1.4 Distinguishable