How do I use CSS to modify Panel widgets' style like fontsize and color?

[ahuang11]

import panel as pn

css = """
.bk.bk-input-group label.bk span.bk {
  background-color: lightgray;
  color: red;
  font-size: 250%;
}
"""
pn.extension(raw_css=[css])

pn.widgets.RadioBoxGroup(options=['a', 'b'])

the CSS tags are from browser console.

1. First right click, inspect
2. Use the element select tool
3. Click on the element you want to edit
4. Read from the console what the tags are
   
5. use that to construct your CSS:

css = """
.bk.bk-input-group label.bk span.bk {
  background-color: lightgray;
  color: red;
  font-size: 250%;
}

6. Google CSS style keywords

I think this should be documented somewhere