Changing the background colour shouldn't delete or unlink an AD/LDAP account, did a sync happen with the AD server at the time you changed the client colour?
If you unlink your AD/LDAP account it doesn't just delete the user so I don't believe it happened because of that.
LDAP sync in our envoirment happens at midnight. So when me and the other technican came in, our accounts were normal user accounts and if you searched helpdesk for our calls you could see our old users with a [D] next to the name. We didn't unlink our AD accounts or do anything else to our accounts besides changing the background colour.
If you change the colour back and forth a few times, do you find this issue occurs again and again?
If so, I recommend contacting support for assistance.
If not, it might have been a one-off accident that just so happened to be at the time the colour changed.