Creating Legends for a Custom Visual

I am trying to create a custom Bar Chart using Typescript.

The sole aim to create this visual is to have custom legends that can have font size below 8px and can be customized through CSS.

I wanted to know if it is possible to apply CSS to legends in a custom Visual. If so, then what is the syntax for creating the legends and then adding CSS classes to it .

I am following this tutorial for the reference - https://www.youtube.com/watch?v=zLNfXxDsa-s&index=14&list=PL6z9i4iVbl8C2mtjFlH3ECb3q00eFDLAG

Thanks