Does a Lawful Permanent Resident have to pay a tax when buying real estate?

The Alleged Tax

Two years ago, my wife (US Citizen) and I (Permanent Resident) bought and moved into a house in Colorado (Greeley, Weld County). At closing, we were just about to put both our names on the paperwork, when our realtor told us that "a non-citizen will have to pay a tax", and that it would be … I don’t remember if she said 20% or 10%, but high. Either way, more than we could afford, and we were signing, pens in hand, so only my wife’s name went on the deed and we thought we could always change it later. (I did some googling after to try and find out more about this tax, couldn’t find anything, then we had a baby and forgot about it.)

Now we are moving to another city (Pueblo West, Pueblo County), selling this house and buying another, and I have been trying to find what this tax is and how much it would be, as I would like to be on the deed jointly.

Colorado’s Non-Residency Tax

I cannot find evidence this tax actually exists. The closest I have found is a Colorado State tax for non-Colorado residents. (https://mountain-living.com/blog/not-living-in-colorado-will-cost-you-2-more-when-you-sell-your-vacation-home/) But I am a Colorado resident, and that tax is for selling a home, we were buying. (Although now we are doing both).

I’m wondering if our previous realtor misremembered badly? It was a sudden "oh, you’re aware of this, right?" kind of thing verbally, at the signing; not something formal or in writing. Or was she right, and there is a huge tax I/we’d have to pay, and I just can’t find it online? I have been through about a dozen Google pages of various search terms, and searched on StackExchange.

Other Details

I am a LPR (conditions still on card), British origin, have a SSN, and my wife and I file taxes jointly, although I do not have any income myself. This and the new house would both be our primary residencies, and are still in CO.