For what it's worth, Google recommends using pixel units for font sizes: https://developers.google.com/speed/docs/insights/UseLegible...

I personally use a base font size in pixels and use em units to increase or decrease relatively.

I don’t want to start a flame war of any kind here but I did want to state that I very much dislike googles designs, I find their UIs very hard to navigate and generally ‘displeasing’ to the eye.

For colors and contrast, use something like http://paletton.com/ where they have it set up to show a color scheme for multiple types of sighted issues.

For fonts and text; the Google guidelines aren't awful, assuming you're not hand calculating your px and use em (they talk about it, but it's extremely brief).

Or were you asking about something completely different?