Overlay icons are small images affixed to the periphery of your file/folder icons which can allow you to at-a-glance tell whether or not a file has been backed up.
If you are not seeing SpiderOak ONE's overlay icons in the Windows file explorer, begin by confirming that ONE is set to display them. In the SpiderOak ONE application on your computer, open Preferences - General and enable "Display File & Folder Overlay Icons" if it isn't already, then press Save. If it is enabled, then disable it, press Save, then return and enable it again, pressing Save once again.
If that doesn't work, then the problem is usually due to a conflict with existing overlays from other software, as Windows will only allow you to register a limited number of overlays. Review the other software on your computer and temporarily deactivate any overlays they have. You will probably need to reboot your computer before you see results. For more information on managing icon overlays, see:
If you do not wish to have the SpiderOak ONE logo overlay the icons of your backed up files in the Windows file explorer, you can turn them off. In the SpiderOak ONE application on your computer, open Preferences - General and un-check "Display File & Folder Overlay Icons". Then press Save.