Roster class colours have displayed to left of a time entry in TimeTrak Professional if a roster class colour is set since 21.2 as per below:
https://timetrak.co.nz/blog/category/timetrak-21-2-release-notes-whats-new/#Point5

These colours were added to TimeTrak mobile and the TimeTrak APP from version 21.2 as per below:
https://timetrak.co.nz/blog/category/roster-class-colours-now-available-on-calendar-in-mobile-and-app-for-time-entries/

From TimeTrak version 23.1.1, Approval by user and Approval by Job reports have been enhanced to match this functionality displaying both the billable status colour as well as the roster class colour against time entries in order for approvers to be aware of not only the billable status but the pay rate they are approving.

Approval by User:

Approval by Job:

Note: Disbursements and allowances recorded do not display a roster class colour.