The colour purple has been chosen for a part in the latest attempt by the Public Fundraising Regulatory Association to improve the image of face-to-face fundraising.
The association has decided that appointing team leaders and making them identifiable could improve relationships with council officials and town centre managers.
This week, more than 30 team leaders sporting armbands in the PFRA's signature colour of purple will lead their troops onto the streets of London for a 12-week trial.
Nick Henry, the PFRA's head of standards, said the idea came from meetings with local authorities about site management agreements.
"Some officials have suggested to us that it would be useful to be able to identify the person in charge of the team in cases of breaches of agreements, such as fundraisers straying outside the site delineation," he said.
Patrick Rigabie, operations manager for street management at Westminster City Council, said he thought the armbands would help the public to know who to approach when they had a complaint about a fundraiser.