Within Teamwork, you can pick a new color theme that will show in the header area of your site.
Click your profile icon in the top right corner of your site, and select Settings from the dropdown menu.
In the Settings area, go to the Color Theme tab.
You can choose one of the preset colors on the left, or set a custom color on the right.
When setting a custom color, you can either enter a hexcode value or use the color palette.
When you click any color, you will see a preview of that in your site header. Click Save Changes to update your site theme.
For more information, see: General Settings