According to Official Guinness Records,
The most hair dyed in 24 hours - single location was 380 and was achieved by Schwarzkopf Professional and Sergio & Margarida Hair Salon in Lisbon, Portugal, on 21 October 2009. The record was achieved by a team of 10 professional hairdressers and their assistants.
For a complete list of 2009 records, please visit 2009 Guinness Records in Portugal.