White portals always take you to an Ultra Beasts world,

Red portals take you to the Ultra Space cliff area. These have flying type Pokemon such as Altaria.

There's also a yellow portal which takes you to the Ultra Space deep cave area. This holds types which I'm unsure what the theme is. It includes Medicham

The green portal takes you to the Ultra Space flat cave which I don't know which types it gives yet. It has Helioptile in i

The blue portal takes you the the Ultra Space lake area which has water types such as Barbaracle and Quagsire.

All of the Ultra universes you land in are called "Ultra Space Wilds" apart from Ultra Beast lands.

The amount of lightyears away is how deep through the Ultra Wormhole you go.