Most CSS changes, especially changing colors, you want to accomplish can be handled through the Page customizations in Design / Blocks. However, if you need to add custom CSS this doc will show you how.
This doc covers template, block, and custom CSS and how to apply it to your Blox CMS wesbsite.
The CSS class field can be used to make a block visible or hidden based on a device's view size (desktop, tablet, phone). This is useful for l…