How to customize Google Calendar with CSS?

I have a iframe with Google Calendar:

<iframe name="iframe1" id="iframe1" src="https://calendar.google.com/calendar/embed?height=600&amp;wkst=1&amp;bgcolor=%230c4da1&amp;src=example.com" style="border-width:0" width="800" height="600" frameborder="0" scrolling="no"></iframe>

Doubt: I can customize Google Calendar using CSS? If not, I can customize otherwise?

I would like to change font size, color, etc.

from How to customize Google Calendar with CSS?