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.
Koa11y - Automatically detect accessibility (a11y) issues on webpages
Who Can Use - WhoCanUse is a tool that brings attention and understanding to how color contrast can affect different people with visual impairments.
EIII Checker Suite - The checker services can help you to locate and remove barriers on webpages or in PDF-documents.
Kontrast - Check and adjust web element contrast in real time.
Palette For Mac - A menu bar based colour contrast analyser