This feature is only available to Admins
Once assessments have been created, the colors and labels can be changed any time by the admin.
To edit assessments, click on the three dots next to your name in the top right of the page and select Assessments from the dropdown.
On the Assessments page, just click in the box to edit the name of the assessment level and click on the color box to change the colors. Make sure to click Save Changes when finished.