LOL... only Greece is above yellow rating?
Yep. There is a detailed report that goes along with the image that explains their criteria, but it takes into account things like the predominance of CCTV, the use of biometric data (i.e. DNA databases), wholesale spying on the public (i.e. warrantless wiretapping, the UK's proposed database of every electronic communication transaction in the country, etc.) OTOH, all the grey countries are areas which were not included in the study, I think due to lack of information. It's likely many of those would be green simply due to lack of funds for the technological and staffing requirements for a decent Big Brother society like the US, China or the UK.