CO law will apply. Unfortunately, CO is a Several Only state, which makes things more complicated. All the more reason to let your insurance company handle it. Ask your insurance company if they will agree to waive your deductible, since they know they'll be getting 100% of the money back, assuming everyone that hit you has sufficient limits of liability. The state minimum allowed for property damage liability limits on a policy is $15k. The primary issue for them to deal with is which party pays which % of your damage. Your last description of the accident should make that easier, since it wasn't just one car rear-ending you, and then another car hitting that car and pushing it back into you. 2 distinct impacts in 2 different locations on your vehicle is pretty straightforward.

Your vehicle sounds like a total loss. If the first impact alone was sufficient to total it, they will owe you for your damages, and the second vehicle will only be responsible for whatever the decrease in salvage value was as a result of them hitting your already totaled vehicle. If the first impact by itself did not total it, each person is responsible for the same portion of the total loss as they caused to the vehicle. For example, If the car is worth $30k, car #1 caused $20k damage, car #2 caused $10k damage, car 1 owes 2/3 of the total loss, car 2 owes 1/3 of the total loss.

It gets more complicated if one or both parties don't have sufficient limits to pay for their portion of the damages.