Depending on where it came from there might not be a vin. Wyoming only started requiring/assigning a vin to be stamped on home made trailers in the past couple years. Check the title for a VIN#. If the title and there is no VIN on it you will have to be assigned one by CO DOT which will start a big process. If you can't find it on the trailer and there is one on the title just stamp it on the trailer and get an inspection done.
If there is no VIN Wyoming makes you go through the following process: (hopefully CO process is similar)
1. Get a VIN inspection to verify there is not one on the trailer.
2. Go to DOT and get one assigned to the trailer (bill of sale and photos required)
3. Stamp VIN and get another inspection.
4. Go to County Clerk and get a new Title issued in your name
5. Pay Taxes and Registration
I wouldn't even tell them its for a boat and the title and bill of sale should have the "Amount" you paid for the trailer on it and should suffice as a receipt. Its so you can pay taxes on it. If there isn't an amount paid filled in on the title just tell them you paid $1 for it.
If there is no VIN Wyoming makes you go through the following process: (hopefully CO process is similar)
1. Get a VIN inspection to verify there is not one on the trailer.
2. Go to DOT and get one assigned to the trailer (bill of sale and photos required)
3. Stamp VIN and get another inspection.
4. Go to County Clerk and get a new Title issued in your name
5. Pay Taxes and Registration
I wouldn't even tell them its for a boat and the title and bill of sale should have the "Amount" you paid for the trailer on it and should suffice as a receipt. Its so you can pay taxes on it. If there isn't an amount paid filled in on the title just tell them you paid $1 for it.