title: Remove Angular Material Theme
body: <p>I started building the front end of my web application using the angular material "Indigo-Pink" theme. Now I want to switch to a custom theme but am not sure how to do that. In particular I don't know how to remove the old theme. I was able to install the custom theme without removing the other theme, but this does not seem like particularly clean solution and I fear it might lead to problems later on.
  How would I remove the old "Indigo Pink" theme the right way?</p>
  
  <p>Thank you very much in advance!
  Any help is highly appreciated!</p>
  
  <p>Best regards, 
  Sam</p>