Who Can Use - WhoCanUse is a tool that brings attention and understanding to how color contrast can affect different people with visual impairments.
Site Palette - Get the essential colours from any website
Cron Color - Free web tool for designing color palettes and checking contrasts.
Color Palette Generator - Enter the URL of an image and find its color palette
Kontrast - Check and adjust web element contrast in real time.
EIII Checker Suite - The checker services can help you to locate and remove barriers on webpages or in PDF-documents.