Type about:preferences#advanced<enter> in the address bar. Under Advanced, Select Update.

[v56+] Type about:preferences#general<enter> in the address bar. Select Update.

Select Never Check For Updates.

Also turn off Use a background service to install updates

Hi niko, something like a green/purple color on videos? Could you check the solutions in these recent threads:

• why are online videos green and purple since the latest Firefox update?
• Youtube video Purple and Green

Note that this should be fixed in Firefox 57.0.2.

• Help -> About Firefox

You can find the full version of the current Firefox release (57.0.2) in all languages and all operating systems here:

• https://www.mozilla.org/en-US/firefox/all/
• https://www.mozilla.org/en-US/firefox/57.0.2/releasenotes/