Green address bars/lock-backgrounds are used for sites which use an extended validation certificate. With the cheapest certificates the issuing organization only checks if the requester has control over the domain. With an extended validation certificate the issuer also checks the address and other business information of the proposed certificate owner. with an extended validation certificate you therefore not only know that the traffic to the site is encrypted, but also that the site and site owner are legitimate.
It is not only Chrome which turns green. All modern browsers use this method to show the use of an EV certificate.
Wasn't there one of the certification companies offering this service a few years ago? It was something like you had to download their toolbar and then when you went to a site which paid for the service and was legitimized, the url bar turned green.