How do I turn off my apple tv?

You don't. It goes into standby/sleep. You can access by going to the settings or press/hold select on the remote for 5 secs

This answer is not correct. My universal remote recognizes the apple tv and when I power off all devices the apple tv immediately turns off. There is a command to do this, clearly, but I don't know what it is.

That command is simply putting it into standby/sleep mode.

That would be obvious. The question that isn't answered is how to do that.

I already stated above how to put the device into standby/sleep. The question has been answered and the OP is long gone. You are now replying to a year old thread, your remote is not turning off the device.

I see, I misread your answer.

It turns off by its self.

The wight light is off (Apple t.v.)

Press any button on the remote to

Turn it on

The light is off, the device however is in sleep/standby mode.

Well, now I've tried the method of holding the "select" button down for five seconds or longer, and it doesn't turn the machine off (or standby).

This is not a big deal, more a matter of curiosity and maybe I want to be like the big boys who sell universal remotes and program something to control it myself someday (yeah, whatever).

Are you using the bundled aluminum remote? Is it properly paired to the device?

Yes, it controls it normally, but holding down the select button doesn't power it off (or turn the light off).

It won't power it off, nothing will. It will be in sleep mode unless you physically unplug it. However, the light should go off and I just verified on my system. Are you receiving any feedback when you hold the select button ?

There is no off. That is an oudated concept with always on devices that have to stay connected in sync. You can put it in "sleep" mode with Settings > Sleep Now but that really just turns off the video card. ATV is still on. The only off option is to unplug the power cord.

Yeah, no off. The little blue light is on. Lighting up the room. Potentially aggravating spousal unit. Doesn't need to make sense, but I would like to turn the stupid light off when "I" want to turn the stupid light off.

If holding select isn't working then just put to sleep via settings - sleep now