After rupture achilles tendon surgery my fourth toe is black and blue, is that normal?

Difficult question: I have never seen that in all my years however a bruise can occur due to gravity pooling blood anywhere. If its painful or any type of drainage u should report it to your surgeon. How long ago was surgery? Did you get a block behind knee? These could be factors.

Can happen: Blood once it is out of a blood vessel just goes to the lowest point. (you pour water into an upright glass it goes to the bottom). A rupture of the achilles tendon as well as the attendant surgery can causing bleeding. If you do not keep the foot higher than your heart or dangle it too much it follows the path of least resistance and can end up in your toe(s).

Possible...: I had a similar problem following a sever ankle sprian two years ago. It went away after only a few days. If it becomes worse, have it evaluated by a professional.