You may access your colleagues' tickets by selecting 'Organization Tickets' in the 'Ticket View' tab
When you access the 'View My Tickets' page from the Service Portal, you can choose from the 'View' tab in the top right-hand corner and indicate whether you only want to see the tickets you have entered or all the tickets that have been entered on behalf of the company you work for.
In this way, by selecting 'Organization Tickets' in the 'View' tab, you can see all the tickets you have entered as well as those entered by your colleagues.