The former Pussycat Dolls star wore a wacky turquoise hairpiece while veteran actress Lumley sported an auburn style to support CLIC Sargent's Wig Wednesday fundraiser, in aid of youngsters battling the disease.
Roberts says, "I had a great time with Wig Wednesday. It was a lot of fun picking out my wigs and trying out lots of different looks - and to be doing it all in aid of the U.K.'s leading cancer charity for children and young people was even better. Hopefully lots of people will get involved with Wig Wednesday and it can raise a lot of money for CLIC Sargent."
Lumley adds, "Being diagnosed with cancer is a frightening experience. The gruelling, often life-saving treatment involved can last up to three years and frequently leads to children and young people losing their hair. It would be great if you could join me in showing your support for them by getting your wig on and raising money for CLIC Sargent."
The initiative, which is also supported by British actress Michelle Ryan and Dj/Tv presenter Laura Whitmore, takes place in the U.K. on 22 May (13).