The Harris Museum and Preston Minster were lit up on Saturday evening, along with other buildings across the country, in an event called Purple Lights for Hope.
It was suggested in Preston by Caz Kay from Lostock Hall, who has lost three members of her family to pancreatic cancer.
She said she wanted to raise awareness of the illness, and described the weekend’s events as “fantastic”.
Mayor of Preston Coun Nick Pomfret helped to organise turning the Harris purple after Caz had contacted him.
He said: “It’s something that could affect us all, and people aren’t really aware of it.
“I tried to get the wheels in motion and the Town Hall pulled out all the stops to get it lit up. Caz was over the moon and so was I.
“It will attract people’s awareness towards it, it might make people look for symptoms and go to the doctors earlier, and could ultimately save lives as well.”
For more information, see www.pancreaticcancer.org.uk.