It's not possible to remove the purple circle in the version for Firefox on Android. The thing is useless and should be off by default anyway. Good add-on otherwise. Unlike ad blockers it blocks both ads and trash scripts that websites are clogged up with, and it does it without using any resources. Speeds up browsing so much it was the only way to use a 2004 laptop for internet. Some people say it sells your data but I couldn't care less about that.

Edit: What I said was assuming you turned off the new three options "enchanced blocking" and the other two in custom setup. If you blocked the trackers you wanted to block then those options don't serve a purpose and they slow things down.