Hi,
As charts are based on plotly you can use the styling options defined in the docs.
Here is a link to what you are looking for: https://plotly.com/javascript/reference/bar/#bar-textfont
You can also play around with the basic styling options using Plotly Chart Studio
If you never worked with anychart / plotly I would reccomend you watching this video to learn more about how charts are built up and how to customize styling: Video1, Video2
Hope that helped.