Telekom Farbverwendung - PDF on telekom-cg.com which lists the Telekom color definitions. I only found it there, it looks official. Interesting is the sentence about where the web color comes from: "The hexadecimal value (www) conforms to the global norm and is taken from the 'Websafe Color Library'" - it sounds more like it was selected after visual inspection and is closest to RAL 4010 (which is ultimately a color tone specification rather for print or coating) (sRGB is not that big).