You can add mobs to teams with /scoreboard teams join Red @e[type=Pig] for example, but the mobs nametag won't change to the color of their corresponding team.
Linked issues
is duplicated by 4
MC-50477
Mob's Names do not change color when added to a team with a certain color already defined.
Resolved
MC-53246
Entities team-color/scoreboards not showing?
Resolved
MC-61977
Non-Player entities don't get team prefixes!
Resolved
MC-62446
Entities custom names are not affected by team colors
Resolved
Comments 3
You should probably edit this and put more information like how the scoreboards you ou under the nametag doesn't seem to appear for entities, putting health, a kill score or any type of score for that matter won't appear under the persons or entities name tags.
This is a duplicate of MC-46956 which has been marked "working as intended"
Searge in the comments below https://bugs.mojang.com/browse/MC-46956?focusedCommentId=171791&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-171791
"It's currently not planned to apply the team options to any entities in a team."
Can confirm this. Would be a great feature to have this in the game if it is not already implemented.