WOW Colorado shipping can be complicated!
The long and the short of the point... USE UPS IF YOU ORDER FROM US. USPS from this state is hard to deal with and FEDEX also has a bad track record here.
USPS - Colorado only has 1 sorting center for ALL of Colorado and Wyoming. The only packages I think will even begin to make it efficiently is Air Mail from here. I would not use USPS. I do so sometimes when speed is not a factor or it is requested specifically. USPS pays their carriers and employees the least of the 3 major providers. The positive side here is that the postal workers here do seem like they're in good moods despite the efficiency of the mail here and their rate of pay.
FEDEX - I can't begin to describe the issues I have with FEDEX shipping from this state so I'll just leave it as this is the last option you want. Their utilization of contractors and outsourcing, as well as their rate of pay ensures no quality in package care or delivery.
UPS - The big winner of the best shipper contest. 95% of the time shipping and receiving is smooth, tracking lost packages is easier, and this is generally how I ship everything if I can help it. In some places like New England, it is just as efficient to send USPS since UPS can take 7 days.