Colorado does have part-year resident tax returns. You file the regular DR 0140 and include, in addition to any other schedules, DR 0104PN to show the split of income between CO and the other state and to calculate the proportionate tax due to Colorado.
Colorado does have a special Senior Housing Credit for 2024 which is available for part-year residents. The requirements are that the taxpayer and/or spouse are 65 or older at the end of 2024, do not already have a property exemption for living there for 10 or more year, and don't make more than $75K AGI ($125K for joint returns). The max is $800 which tapers down to zero at the AGI limit and the amount of the credit for part year residents is reduced proportional to the income from CO.
