"The individual maintains a permanent place of abode in Colorado and spends, in aggregate, more than six months of the tax year in Colorado." is a statutory (as opposed to domiciliary) resident. Federal Law - 4 U.S. Code § 114 - (a)"No State may impose an income tax on any retirement income of an individual who is not a resident or domiciliary of such State (as determined under the laws of such State)." would be the best application of why Colorado would not be able to tax your retirement.
Just to note: If your "other" state is one that does not tax the income either, so Colorado MIGHT try to establish your domicile as a pretext to avoid taxation (but once again, this is trying to prove intent using inferences). As a practical matter, the amount of time and effort may not be worth it on the part of Colorado.
@banjo1000
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