I always advise my clients to wear neutrals and to stay away from crazy distracting patterns or clothing with words on it. However, it does totally depend on the vibe you are going for. If you are doing a branding session and your brand colors are bright and colorful, then that is totally okay. I will never force you to wear anything that you are not comfortable in. I also have outfits guides and Pinterest boards that I send to all of my clients who need help.
I am also always available through Facetime/call/text/email. A lot of clients like to send over their outfit ideas and ask for my opinion! I will always be available to answer any questions that you may have!