The idea is to help induce synesthesia between words and colors, so that when you see a word you think about it in a particular color. Not only has this been proven to increase verbal memory but now just the visual of a word has a color connected to it. With reading as an essential daily function imagine making your day just a bit more colorful :)
I also wrote a medium article on synesthesia and why I built this (https://medium.com/@ilianherzi/inducing-synesthesia-4ead16f37a1b).
Couple of things about version 0.1.0 of the extension:
0. The current version is best used on webpages that don't update or change with a lot of text (so when reading).
1. For dynamic pages that update the color changes don't persist, so for example in gmail colored words go back to black and white.
2. On input text the color of the words don't change (so typing an email, writing a post, searching on google)
These difficulties with the extension will be fixed in version 0.2.0!