As part of an atherosclerosis addition to MSI's "Heart" exhibit a few
years ago, we put toghether large tubes filled with clear mineral oil (I
believe) and red glass nuggets (to represent RBCs.  (Our object was to
show how narrowing of blood vessels obstructred flow.)  You face an issue
of scale in that the red color of blood is due to many, many RBC's.
Maybe if you could find pin-head sized red glass beads you could put
enough in that shaking would give an overall impression of a red fluid.
I'd be happy to discuss this further if you'd like.
Ethan Allen