If they're in an open stock trailer keep face masks on them.
Depending time of year, they may need sheets or blankets.
That's approximately a 950 mile trip. In good weather you could push that and make it in one day. I wouldn't try it in the winter because you don't know how clear the roads will be. I would plan on one layover for sure during the winter. Were it me, I would plan on one layover anyway - lol
Keep good quality grass hay in front of them at all times. I would either stop the grain altogether or cut it way back.
Offer them water when you stop for gas. Not from the gas station water hose either - lol
Do NOT let them out of the trailer until you get to your layover or destination. They don't need out of the trailer to exercise or anything else as you never know what could happen to cause an accident or to cause even the most seasoned of haules to not want to go back in the trailer.
Carry enough hay to transition them after you reach your destination.
Have a tube or two of Banamine in the glovebox and maybe some Bute. It would not be fun trying to find a vet along the way.
Have your Coggins and shipping papers current, thru your vet. Tell him where you are taking the horses, so he can be sure they have the necessary shots to go into Colorado.
Have the truck and trailer serviced - especially have the bearings checked and greased, if needed, in the wheels on the horse trailer.
If you want to look for a layover mid-way thru your trip, I highly recommend www.horsemotel.com
I used them for every stop coming back from SoCal to TN and my back yard trail horses were treated like royalty at every layover.
That's all I can think of for now, except don't baby them like they are dogs. I hauled three of my four from PA to SoCal then to TN five years later, in my 4-horse open stock. I had a double wooden floor in my trailer with mats on top. I did not use shavings, I did not wrap anybody's legs but, nobody had leg issues either.
To reiterate, they all wore flymasks the entire trip.
Hope this helps