I don't think Hamas has an official uniform. I'll note that, when Hamas wore regular camo,
Israel's i24 News and The Sun in the U.K. claimed that “the terrorists wore our uniforms” and “sick Hamas terrorists used IDF uniform disguise.” source
And now that they have someone in Hamas not wearing camo (I don't know, does Gaza even have a working laundry at this point), both the Israeli media and The Sun immediately switch to
Hamas using the civilian population as human shields. Dressed in jeans and a casual grey shirt to look like a civilian
So basically they're saying it doesn't matter how Hamas dresses, whatever they wear is an evil deceitful attempt to mislead the pure upstanding Israelis.