Stylesheet customization options
If you have coding skills, especially CSS, you can do more changes in the stylesheet:
Design Manager > Coded Files / custom / system / css / Instinct-Theme.css
There are also a few HubL variables at the top, so you can easily change the default theme color, harmonic color and links color:
You can also find variables for font families, corner radius and more:
You can explore and learn more about the HubSpot tools and features in the official HubSpot Academy.