If purchased at a hardware store or garden center, they are suspect and likely full of pesticides. If they are labeled for decorative use, I would skip them. If they are labeled for human consumption, then they are fine. All depends on the soil they are grown in and what chemicals have, or have not, been applied.
Around here, they call it "ornamental cabbage" and not fit for consumption. Probably best to skip. I would not put it past some stores or sellers to spray them with plant paint to make them look better.
Now, if you know the grower or grew them yourself with no pesticides or treatments, by all means should not be a problem!