Can I change the default colors for ticket status?

The color of the text for the ticket status can be set from 

Admin CP > Tickets > Statuses > "Select Status" > General Tab > Status Color.

Similarly, the background color of the Ticket Statuses can be setup from 

Admin CP > Tickets > Statuses > "Select Status" > General tab > Status Background Color. 

Background color is used for the "General Tab Bar" when viewing the ticket.

 

The color of the text for the Ticket Priorities can be setup from :

Admin CP > Tickets > Priorities > "Select Priority" > General Tab > Foreground Listing Color.

The background color for the Ticket Piorities can be setup from:

 Admin CP > Tickets > Priorities > "Select Priority" > General tab > Background Listing Color.