Wear what you are comfortable in, and what best represents you. I usually tell my clients that bold patterns tend to be too busy in an image because when someone looks at your portraits you want their eyes to look at your faces first, not your striped dress or the writing on your shirt. Darker colors are always more flattering than white, unless you're super tan. And unless you absolutely love your arms, don't wear anything sleeveless. Those three guidelines will keep most clients from accidentally wear something they might later regret.