What's the penalty in Colorado for possession or possibly selling pot as a minor?

Listen kid be honest, your the person who was caught. It's fine. I mean your going to be facing some jail time if you had a qp unless you miraculously have a medical card or this is your first offense your friend could be looking at about a year and 2-3 years of probation. Here in texas my brother got caught with a half ounce and got 18 months probation as his first major offense.

 

If you're under 18, you'll get a slap on the wrist and some juvie probation.
Hell, I was arrested four different times when I was seventeen for a combined total of twelve different charges (assaults, destruction of property, retail theft, etc... no drug charges, though) and I only spent a week and a day in lockup. That's the grand total, not the time spent with each arrest.

They gave me 30 days of house arrest on two separate occasions. I didn't have an ankle bracelet, and the trackers didn't come after 9, so I was constantly leaving my house.

I fucked off my probation so hard that it was extended until I was 21 (the beginning of this year).

I ended up lucking out and getting a brand new judge's first case for my last charge and talked my way off probation. All I had to do was pay a $200 fine.
The only charge I had on my record was the one contempt of court that I received after turning 18, and that was expunged when I paid my fine and had my probation severed.

Then again I'm in Utah, and I'm pretty sure that was just one of those very rare times in my life where I am, literally, one of the luckiest people alive.

 

I'm sure your friend will end up facing a week or two in jail and probation time or just a slap on the wrist and a fine. However if he was caught selligpng with a half pound and they consider it selling hell definently get a few months. And if it was on school grounds...ha he's fucked.

 

I can tell you that if he's not 18, he won't be charged as an adult (unless the crime is violent in nature) and he won't spend a second in jail.
Juvenile detention, however, is a real possibility. Sucks if it comes to that, because juvie is worse than jail and prison. (I don't know from personal experience but I have quite a few friends that do. That's where I get my basis for that statement.)