Color Contrast Testing
Color contrast testing verifies that text and important visual elements have sufficient contrast against their background to be readable by users with low vision or color blindness, measured against specific ratio thresholds defined by WCAG (typically 4.5:1 for normal text, 3:1 for large text).
Contrast ratio is a precise, mathematically calculable value based on the relative luminance of the foreground and background colors — automated tools can check it exactly against the WCAG thresholds, making this one of the most reliably automatable accessibility checks, unlike more subjective concerns like alt text quality.
It's a surprisingly easy standard to violate unintentionally — light gray text on white, a popular minimalist design choice, very often fails the 4.5:1 threshold, and design systems increasingly bake contrast-compliant color pairs directly into their tokens specifically to prevent designers from reaching for a non-compliant combination by accident.
