Hmmm, this is an interesting little thread? However, what about purple vetch? Horses love it. Lots in the spring. Color doesn't seem to matter to any of my horses w/that plant. However, I was told that plant is later not safe for them once it has the seed pods. Only allowed to eat in the spring. Sure do have pretty purple flowers!
What one of my mares does do though, not plant related, is in the spring she seems to look for snakes! Wooden sticks, branches, etc she takes a double look at! ahahaha...Especially if it is curvy!!! lol Makes for an interesting ride. Behavior always begins in early April too!!! Maybe her way of saying "April Fools" to me! hehehehe