As far as I know, Colorado has no laws about fender sizes and tires sticking out.
For other reference, these are a good summary of lift laws and other 4x4 related stuff for all 50 states.
http://groups.msn.com/Bronco2Rangerclub/liftlaws.msnw
http://www.truckworld.com/How-To-Tec...lift-laws.html
Other good laws to know for 4x4's in Colorado:
42-2-119: you have 10 days to notify the DMV of any address change or name change. Failure to do so is a class B traffic infraction.
42-2-107: you have 30 days to get a Colorado drivers license after moving to Colorado.
42-2-115: you must give your license to any peace officer that askes for it if that officer believes that you have, are, or will commit any traffic violation. This means that you must remove it from any billfold, purse, wallet, container and hand it to the officer. Failure to do so is a class 3 misdemeanor traffic offense.
42-4-201(4): no vehicle shall be operated unless the drivers vision through any required glass is normal & unobstructed. Weak but usable if your windshield is cracked.
42-4-205: every vehicle will have at least 2 operating head lamps, height not to be more than 54" or less than 24" from the ground to the center of the lamp. Class B traffic infraction.
42-4-205: tail lamps (2) visible from at least 500' at a height of no more than 72" or less than 20". Also, a lamp that illuminates the rear plate visible from a distance of at least 50'. Class B traffic.
42-4-212: auxiliary lamps. No more than 2 floods (spot), 2 fog, 2 passing (side), and 2 driving. Fogs must be mounts between 12" & 30", passing between 12" & 42", driving between 16" & 42" all from the ground to the center of the lamp. Class B traffic.
42-4-215(6): no more than 2 back up lights. Can not be use while vehicle is in forward motion.
42-4-215.5: blue dots are allowed on street rods and custom motor vehicles.
42-4-219: while on any roadway, no more than 4 total front lights with a combined beam intensity of 300 candlepower.
42-4-226: mirrors. Every vehicle shall have at least one mirror. If there is no rear and rear side windows, that vehicle will have a mirror on each side.
42-4-227: tint, no less than 27% light transmittance, windshield & front sides no less than 70%.
42-4-228: tires, no less than 32 seconds of an inch depth. Of note in this section states that it is a class 2 misdemeanor to sell a vehicle intended for on road use with bad, bald, sliced, etc. tires.
2-4-233: alteration of suspension system. No person will operate a registered vehicle on any roadway "with either the front or rear suspension system altered or changed from the manufacturer's original design except in accordance with specifications permitting such alteration". Basically, install an aftermarket lift, you're ok. Switch your coil springs to leafs, violation. This section does NOT apply to motor vehicles designed or modified primarily for off-highway racing purposes.