Brand Colors for Team
If you're a Team user, you'll first go to your Team dashboard via your username in the top right.
Ensure you are in your Team dashboard, then, go to Brand Assets → My Colors in the same menu:
You can select up to six colors for use across your team’s visuals.
Any member of the team may add, edit, or remove colors from the My Colors selection, and may use the selected colors when designing a visual or creating a color scheme.
Learn more about Brand Colors here