Because it's not your computer screen, it's the psychedelic colors on Tracee's dress. These two colors are close to impossible to combine successfully and should not, I repeat, should not be attempted unless you are a skilled professional. Imagine yourself trying to chat her up at the party while trying not to look directly at her dress. It's hard to focus on it for even a few seconds without getting cross-eyed! She could seriously blind anyone who came within a few feet of her with this wacky color combination. And that just wouldn't be cool at a swank Hollywood party.