If your class and the assignments associated to it are appearing in grey, it may be because you need to provide access to the Classroom calendar.
To allow access, do the following:
Go to the Google Classroom account for your class.
Go to the "Classwork" tab.
Select "Google Calendar".
Once it opens up, it will ask you if you would like to add the calendar. Select "Yes".
Once you do this, you should see your course and its assignments appear in the colour associated to that class.