According to the dev tools docs, you can view the contrast ratio of a text element in the Color Picker as of Chrome 65 - January 2018
However, sometimes the functionality appears buggy, as identified in this thread on Is "Contrast ratio" no longer available in Developer Tools?
Here's an example where the contrast picker doesn't show up
Sometimes adding a background color can trigger it into working again. Has anyone else successfully found a way to get it to work? Are the others tools / recommendations to fallback to if the native contrast toolbox doesn't show up?
Alternative: contrast contrast in FF