Contact Colorado fish & game.
There may be an import application you have to comply with (NM apparently has one, for example)
Anyway - they will know the details.
Cal Kings I think barely touch Colorado. Splendida I think might too. Are there actual specimen vouchers, or just some sight recordings? CO may not consider them native if there are only sight recordings, but their F&G will know.
wildlife.state.co.us/WildlifeSpecies/SpeciesOfConcern/Reptiles/
lists "Common Kingsnake" as Species of Special Concern. So you probably want to call them, lest you get an over zealous officer seizing your snakes in attempt to get the good employee of the month parking spot for busting the evil pot smoking baby eating counter culture snake keeper.
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3.6 L. getula californiae - 16 eggs (Cal. King)
1.1 L. getula nigrita (MBK)
1.0 Pantherophis guttatus guttatus (Corn)
0.1 Pituophis catenifer catenifer (Pacific gopher)
3.3 Elgaria multicarinata multicarinata - 14 eggs (Cal. Alligator Lizard)