While end of session bills cannot have vetoes overridden by the General Assembly, not a realistic chance this year, in any case, with a closely divided state house and state senate, Colorado does not have the pocket veto found in the federal government. In Colorado, every veto must be affirmatively made to be effective. Laws cannot be vetoed simply by not signing them within a specified time period, at a time when the legislature is no longer in session.
The Colorado constitution, Article IV, Section 11 governs the veto process (after session vetoes are governed by the highlighted text):
Every bill passed by the general assembly shall, before it becomes a law, be presented to the governor. If he approve, he shall sign it, and thereupon it shall become a law; but if he do not approve, he shall return it, with his objections, to the house in which it originated, which house shall enter the objections at large upon its journal, and proceed to reconsider the bill. If then two-thirds of the members elected agree to pass the same, it shall be sent, together with the objections, to the other house, by which it shall likewise be reconsidered, and if approved by two-thirds of the members elected to that house, it shall become a law, notwithstanding the objections of the governor. In all such cases the vote of each house shall be determined by ayes and noes, to be entered upon the journal. If any bill shall not be returned by the governor within ten days after it shall have been presented to him, the same shall be a law in like manner as if he had signed it, unless the general assembly shall by their adjournment prevent its return, in which case it shall be filed with his objections in the office of the secretary of state, within thirty days after such adjournment, or else become a law.
The vetoes in a nutshell so far:
SB 01 (prescription drug purchasing pool);
SB 46 (education study committee);
SB 47 (allowing special districts to impose sales taxes to pay for health care)
SB 64 (improved state contracting oversight);
SB 65 (capital construction for schools);
SB 69 (tweaked School Accountability Report format and information);
SB 81 (discrimination in employment on the basis of sexual orientation);
SB 105 (elevator and escalator safety regulation);
SB 111 (cultural competency education requirements for health professionals);
SB 138 (minimum percentage of ethanol in gasoline);
SB 198 (prohibits unfair terms in health provider contracts with networks);
SB 209 (higher education task force);
SB 239 (mortician licensing);
HB 1127 (athletic trainer regulation);
HB 1314 (bans mandatory religious or political propaganda from employers);
HB 1331 (landscape architect regulation);
HB 1336 (uniform athletes agent act);
HB 1346 (insurers must cover the children of dependent children living at home).
HB 1193 (protect patient safety whistle blowers).
SB 52 (allow counties to impose sales taxes to buy open space);
HB 1021 (require PE teachers to be certified or have alternative qualifications).
HB 1212 (allow pharmacists to prescribe emergency contraception);
HB 1174 (require everyone on a construction site to have worker's compensation);
HB 1148 (limits risk shifting to non-responsible persons in construction contracts);
HB 1077 (restrict broad form indemnification in construction contracts).
HB 1056 (healthy snacks in school vending machines);
HB 1010 (governor can't unilaterally join international procurement agreements).
HB 1374 (capital construction for schools);
HB 1371 (disability services report to legislature and study);
HB 1369 (selected Medicaid reimbursement increases).
HB 1023 (require three years teaching experience and master's degree for principals);
HB 1005 (allow voters to approve property tax hikes for full day kindergarten).
There are still about 79 enacted house bills still awaiting action from the governor. And, there are about 80 enacted senate bills still awaiting action from the governor.
Last year Governor Owens vetoed 47 bills from the Democratic Party controlled General Assembly. The chances are good that this year's total will be even higher.