For many years I use to get the John Henry commercial catalog where they also sold plant labels. There was a long list and if you didn't see the variety you wanted you could get them custom printed.
Here are some I remember:
Red
Yellow
Pink
Black
Tomato, yes, tomato believe it or not.
None of them had heirloom as part of a label.
I went to that company b'c I didn't like the new marker pens that Johnny's introduced, as compared with the old ones which I loved, and this company sold the ones I liked but you had to buy a lot of them, which explains why I haven't run out of marking pens in many years.