Vivas trained at the National Art School in Sydney, first undertaking a course in interior design before switching to film animation. In 1969 she went to live in Spain returning to Australia in 1973 to exhibit her Spanish drawings in Sydney and Melbourne.
Vivas undertook work as a freelance illustrator for magazines as well as for children's book publishers. Her style has brought her national and international recognition with her use of muted watercolours, simple rounded shapes and minimal backgrounds. The first children's picture book she illustrated was The Tram to Bondi Beach with Libby Hathorn in 1981.
Vivas has had many successful partnerships with award winning authors such as Margaret Wild with The Very Best of Friends and Let the Celebrations Begin ! (1991) and Mem Fox with Wilfrid Gordon McDonald Partridge (1984) and the internationally successful Possum Magic (1982). She also created her own book Nativity (1986). This title received international recognition as runner up in the Boston Globe Horn Book Awards in 1989.
Vivas has been recognised several times by the American Library Association. The book Let's Eat about a close knit Spanish family was an honour book in the 1997 CBC Awards. It was created in collaboration with her daughter Ana Zamorano.