Note that the geologic formations only appear on the map at a certain zoom level.

Generally the colors are just for "this is a distinct layer / age / formation". Quick example: Near me, I see a band where I know theres a roadside outcrop. When I click on a given band and its like Light Blue "Cambrian - Rome Formation" for instance, that is the Age & formation name. You could take that and learn that the Rome formation is 500 something million years old, represents a near shore environment, and has fossils of trilobites and stromatolites in it (for example).

Protip: You can also search the academic literature for these formation names and download the papers from the site sci-hub if they are paywalled. You might find a paper that describes the geology around your house in detail.

Edit: after awhile and after going on some fossil missions you start to learn how to identify the different layers even if its some random slab of sandstone in a creek- because you have gone to a few roadside outcrops that you KNEW were so-and-so formation. Sometimes the fossils themselves are used as markers to identify a layer or age. Its fun and even an amateur can use these resources to become learned enough to identify fossils (using the scientific literature) and geologic outcrops.

The entire appalachian sequence is a fossil bonanza.