A shift will still marked as red in Client Shift Breakdown if no rate (rate group) has been attached to Client when shift was saved. This means that this particular can only be invoiced once correct rate (rate group) has been attached to shift.
You can fix this by clicking on update attendance icon for client
Rate group can also be added at the time of shift generation from below page.
Note! Please note that shift can also be red if there is nothing to invoice i.e. hours in shift is 0 and program/additional cost along with mileage is also 0.