Contrast ratios calculated using relative luminance per WCAG 2.1 specification. AA requires 4.5:1 for normal text and 3:1 for large text.
AA Normal Text: Minimum 4.5:1 contrast ratio
AA Large Text: Minimum 3:1 contrast ratio (14pt bold / 18pt regular)
AAA Normal Text: Minimum 7:1 contrast ratio
AAA Large Text: Minimum 4.5:1 contrast ratio