I had them on my butterfly weed last year, they are aphids, and they were a mess. Get rid of them as quickly as you can.

Mary

There are several of red-colored bugs around. If they are very tiny and move around very fast, they may be red spider mites too. Most of the aphids that I've seen tend to be clear or white or black, although there are red ones and aphids generally don't move much (ants will carry them).

My horrible aphids were a reddish brown. So small I thought they were a fungus. But Jenny is right, the aphids don't move much. I had to get a magnifying lens to make out that they were actually bugs.