Q.How Tall Do Bachelor Button Plants Normally Get And What Color Are They Normally?
Just curious as I have some that are now at last measure 5’4″ tall. As for color mine are mostly a purple/blue color but I have a couple that are pink. We have not used any miracle grow or anything like that on them. In fact we thought they were dead dead so we threw them in a pile in our yard where there was nothing but rock and shale. It is beautiful back there now. I am actually thinking of putting some little gnome homes out there just for fun. I hope those photos go through.

Certified GKH Gardening Expert
Some can reach taller heights, some can revert, and they can cross pollinate with wild types, as well! I would come to expect many things from them, after they have been in the wild for some time. This collection of articles will offer more information on the plant:
https://www.gardeningknowhow.com/ornamental/flowers/bachelor-buttons