I was just doing the F6 thing to change oufits on a few of my villagers who looked so much alike I could barely tell them apart when I discovered something by accident. I was trying to single out one of my people from a group(hard to do sometimes LOL) and when I thought I got him hit the F6 key to change his clothes. By accident I ended up changing my GC's outit instead! I did not know you could actually change his clothes to something more ordinary, but it IS possible! So, if any of you get tired of seeing your GC in his golden garb and cape, you can change that as easily as you change the outfits of any other villager. I got a good laugh out of that one.

yes, his is the first on the list of male clothes. no other males will be born with these clothes, and you can't get back to them, but they can be changed

I tried the F6 key and it did nothing. What am I doing wrong?

It doesn't work on every villager. I have some that I can change clothes on and some that refuse to change.

You can change a villager's clothes only from the main game screen, when a villager is actually selected, and they can't be wearing the last outfit in the sequence. You can see the entire sequence of outfits in this spoiler thread.