Summary
Minecraft supports the ability to use the team colors as specific sidebars.

This means that multiple players being in the same scoreboard can have different sidebars depending on what color their team has.

Proposed change
is to add new slots for the DisplaySlot enum with sidebar being for specific colors.

Example 
MC1.12 command used to set a display slot for a team color:

/scoreboard objectives setdisplay sidebar.team.green OBJECTIVENAMEHERE

Advantages
The ability to share objectives for multiple players while still allowing team specific sidebars.
The ability to quickly (visually) switch sidebars by changing teams

What would break
Nothing, since the team color support is already added - existing scoreboard plugins will just have another display slot they 'can' use

What would need to change
They way to display slot(s) are cleared or changed, conversion from enum to number (3+chat color)