Color contrast is the difference in brightness between two colors and is crucial for accessibility. It ensures that text and graphics are legible for everyone, particularly those with color blindness or low vision. There are specific contrast ratio requirements: text smaller than 18pt/14pt bold must have a ratio of at least 4.5:1, while larger text needs 3:1. Non-text elements and user interface components should also meet a minimum of 3:1 contrast with adjacent colors. Links that aren't underlined must have a 3:1 ratio with body text and 4.5:1 with the background. To enhance accessibility, use contrast tools and incorporate these guidelines into design practices.
https://blog.pope.tech/2022/11/08/color-contrast-accessibility-requirements-explained/