The band will wear their new uniforms at the concert. This statement is correct. It is not his nor her because it is not referring to one person and the gender is not specified. It is not or because there are not options; it is a fact that the band will wear new uniforms. The pronoun its is not correct because for one it does not have a ' or quotation around the s so it is not referring to multiple things and the band is multiple things.
