What type of test do they do for blood infections , i broke my leg and it gets all red or purple when i stand and blood pools in the foot , ultrasound?

Venous congestion: It sounds more like a venous problem than an infevtion. This is actually quite common after lower extremity trauma. Check with a vascular surgeon. Ultra sound would be indicated.

A blood infection : Is usually when you have something like a bacteria in your bloodstream and this is a bacteremia or you can be septic. What you describe sounds more like you suffered some vascular insult and as a result your circulatory system is not functioning as it should secondary to your injury. You may want to have a vein mapping test performed.