I am not validating what is shown here, but it would make some sense that since ballots in a primary are party specific, you might have indication of what party (not the actual votes inside) the ballot was associated with so that the primary votes get tallied by party reps. I am just guessing here, so I could be wrong. In CO we have to register as either in a party or as an independent, and if you register independent, you dont get to vote in primaries. That is the only reason to stay in the party in my opinion.
I zoomed on the pics.
The ballot is from the June 30 2020 primary.