I do not see it in the list of forms for CO for PS https://myproconnect.intuit.com/releasedates

It appears it can be done online https://www.colorado.gov/pacific/tax/PTC-Forms

No!  The form is available.  My question was, can it be efiled.

I can't say for sure, but if it can be filed and does not go with the prime form, try E-File > Start e-file Other filing types ....