This app is used to measure the contrast ratio between two colors. It can also be used to convert between RGB and hex colors. There are some helpful links to some Web Content Accessibility Guidelines sections that are of note for color-related considerations as well as a link to the WebAIM website which served as the inspiration for some of the app design.
The general design idea was to have a useful, self-contained phone app and not have to switch back and forth between web pages when choosing colors. It also has a light/dark mode and it will remember the last colors you entered (but not if using on the web). There is also some basic error messaging to help if a color code is entered out of range or with information missing.
To use, simply choose a type of color to enter (RGB or hex) for the foreground and/or background, enter the value, and select 'Set Color'. The app will do the math on the color contrast ratio and give a pass/fail assessment for WCAG AA and AAA ratings on normal and large text as well as WCAG AA for graphical objects and UI components.
Hope this is helpful!