Contrast - A macOS app for quick access to WCAG color contrast ratios
Colour Contrast Analyser - TPGi's ADA Color Contrast Checker checks for helps determine the accessibility the contrast ratio of two colors for WCAG AA and AAA.
Hues - The most lightweight color picker for Mac ever
Who Can Use - WhoCanUse is a tool that brings attention and understanding to how color contrast can affect different people with visual impairments.
ColorSnapper - The missing color picker for Mac.
Kontrast - Check and adjust web element contrast in real time.