In recent versions of Chrome and Edge browsers and other Chromium-based browsers, artifacts may appear in the form of colored shapes on the screen due to graphics rendering problems there. These artifacts can show up in many web applications.
This issue is known to Google developers and they are working on a solution. (https://support.google.com/docs/thread/95433575)
You can try the following steps. First, check your browser for the latest updates and update it if necessary. If the problem persists, disable hardware acceleration in your browser's system settings (for Chrome: chrome://settings/system).