Color contrast Testing (CCT)
One of the most important accessibility aspects of a page is the color contrast - it allows user with lower levels of vision to use your application with ease.
W3C, in their Sucess Criterion 1.4.3, explain in details the acceptable levels of contrast - checkout the details here.
Firefox 64 and CCT
When you active the Developer Accessibility Tool, you gain information about the level of contrast of each element in the page, with a simple mark if the passes the W3C standards.
If shows a green check if the contrast is good:
If shows a yellow alert if the contrast can be improved to provide better visualization:
Checkout how to use the new feature on the Developer Accessibility Tools on Youtube: