my therapist doesnt have a "uniform". she believes in being connected to the present moment and chooses what she is most comfortable with at that moment, she encourages her clients to also come to sessions in what ever ways that enables them to be present and comfortable in the moment too.

that said I do know some treatment providers that do dress down by wearing basic grays and blacks due to some clients with some mental disorders can be affected by colors (ie reading posts here on psych central I have read many posts talking about how colors affect them when they are reading posts or have to stay away from some colors due to epilepsy, ocd aspergers atism.....) some people can also get distracted or over stimulated by vivid or clashing colors....gosh there are so many reasons why a treatment provider would dress down by limiting what colors they wear and limiting what clothing or uniform style they wear during therapy...

my suggestion ask the treatment provider. most that I know are very willing to answer this kind of question.