Lumia Cyan update is available for Windows Phone 8.1 handsets and it provides elegant features of Windows Phone 8.1 like a more personalized Start Screen. The two promising features incorporated in Lumia Cyan is Word Flow keyboard and a revamped Action Center. Some more refinement has been done with the Nokia Imaging App, Nokia Storyteller, Creative Studio App.
Lumia 820 is receiving Lumia Cyan update in the UK, Ireland and EU. The country variant is receiving the update. All three Lumia Amber, Lumia Black and Lumia Cyan are available and the latest version is 3051.50009.1424.0004. In Finland and Ireland carrier variants update Sonera and Meteor are available respectively.
The country specific list is available in website of Nokia. You can check if your model can receive the Cyan Update from here. Your phone will notify you if your phone can receive the update. The updates are released gradually for different Lumia models.
You can check the version your Lumia phone is running Settings > About > more information > Firmware revision number.