I found this at: http://www.ncjrs.org/txtfiles1/nij/187085.txt
"Along with these developments, the vory v zakone began to expand their reach and power in the Sverdlovsk region in the 1980s. Throughout the former Soviet Union, the vory had long been regarded as the elite of the criminal world. They were hardcore professional criminals spawned by the gulag prison camps. To contrast them with the white-collar shadow businessmen, these professional criminals became known in criminal slang as the "blues," a name that some believe derived from the blue color of the tattoos that were associated with the vory v zakone. The vory were adherents of the traditional criminal mores developed in the camps and followed a strict thieves' code."