From the Colorado Game Laws
3. MUZZLELOA DING RIFLES
& SMOO THBO RE MUSKE TS
a. Only legal muzzleloaders allowed in muzzleloading
seasons.
b. In-line muzzleloaders are legal.
c. Must be single-barrel that fires a single round-ball or
conical projectile.
d. To hunt deer, pronghorn or bear, they must be minimum
of .40 caliber.
e. To hunt elk or moose, they must be minimum of .50
caliber.
f. From .40 caliber to .50 caliber, bullets must weigh minimum 170 grains.
g. If greater than .50 caliber, bullets must weigh minimum 210 grains.
h. Shotshell primers are legal.
i. Pelletized powder systems prohibited in muzzleloading seasons.
j. Cannot be loaded from the breech in muzzleloading seasons.
k. Only open or iron sights allowed in muzzleloading seasons. Fiber optics
and fluorescent paint incorporated into or on open or iron sights are
legal. Scopes or any sighting device using artificial light, batteries and
electronic gear are prohibited during muzzleloading seasons.
l. Sabots are prohibited in muzzleloading seasons. Cloth patches are not
sabots.
m. Smokeless powder prohibited in muzzleloading seasons. Black powder
and black-powder substitutes are legal.
n. Electronic or battery-powered devices cannot be incorporated into or
attached to muzzleloader during muzzleloading season.
It says sabots are prohibited during muzzleloader season so I would think you would be fine during rifle season for sure.