She got her start in the soap opera The Edge of Night, playing a heiress and former terrorist. In seven months on that show she survived seven murder attempts and ended up marrying her step brother. She followed that role with a longer stint on As The World Turns, originating the role of Margo Montgomery, a character which is still part of that show over twenty years later.
She has appeared on a number of prime-time television shows, starting with Foley Square and several early episodes of Chicago Hope.
Colin has also been in a number of movies, the most successful of which are probably Three Men and A Baby (1987), Independence Day (1996), and Unfaithful (2002).