Definitely a wolf spider (i.e., family Lycosidae). Possibly Hogna frondicola or some closely related species.
The white ball is an egg sac. From Wikipedia:
wolf spiders carry their egg sacs by attaching them to their spinnerets.
You can see similar pictures to your of wolf spiders carrying egg sacs here and here.
Spiderid.com suggests this species has been spotted in Colorado previously:
Hogna frondicola has also been sighted in the following states: Colorado, Maine, Montana.