Colley made her stage debut in 2014 (graduating from her training a term early) as Abigail Williams in The Crucible at The Old Vic in London. Colley received rave reviews and was nominated for a Best Supporting Actress WhatsOnStage award for her performance in the five-star show.
In 2017, she starred as Mileva Marić in Genius, the ten-part television series for National Geographic and Fox 21 about the life and work of Albert Einstein.
