To change the name, colour or subjects for a class, you first need to go 'Settings' then select the 'Academic Years' tab along the bottom.
Then, within your 'active' academic year you are able to view your classes within the 'Classes' tab. Your list of classes should show like this:
From here you can edit a class by selecting the small pencil next to the cross. Within this new window, you should see edit options for the name, colour, and subjects. There is a colour for each subject.