Share your experience!
i am going to answer both of your questions here, http://talk.sonymobile.com/t5/Xperia-M/Xperia-M-google-talk-button-color/m-p/1109959
1.) first are you using the original firmware? not flashed, but the one with the phone came with? if not i suggest you redo your flashing again
2,) if you are using stock firmware, repair your phone using PCC,