I get asked this question all the time from young models of color who want to break into the biz. In my experience, you should not wear your braids or a weave to a casting. Personally, have never worn braids to a casting but I can tell you that when I have been considered for bookings (after being submitted via a photo casting) and we start discussing the look for the show/event/shoot and I tell them that I currently have braids or faux locs… I can almost guarantee that I won’t get booked unless I am willing to take them out and have my hair styled according to their guidelines/desired look. Have I ever taken them out for a booking, YES and I only did it if the pay/project was worth the time and energy to take them out. It sucks sometimes but that is, unfortunately, the nature of the business.
When you go to an in-person casting, more than likely the job they are booking you for is not going to be styling your hair in braids and even if they are, they need to see what the current state of your hair looks like. Most models of color are not wearing their real hair in the first place and if they are it is in an afro (kinky or curly) or it is a low cropped cut.
Wear your hair how you like it. Be sure it is out of your face and make sure it shows off your face in the best light. With that said, I advise against wearing braids to a casting. Braids don’t show off your hair in its current state and if you wear a weave make sure it looks realistic, don’t wear bangs, and be easy on the baby hairs. Also, Stay away from the lime green and other unnatural hair colors.
The key to hairstyles for a casting: make it look as natural as possible even if it is a weave.