Blood is a fine motif to follow throughout Macbeth, but to be honest, I'm not exactly sure what you are asking. Is it, "What is a good thesis statement related to this?" Or "How would I follow this motif to develop a thesis here?"

If it is what would be a good thesis, I'd start by making a bold statement about what blood shows us in Macbeth. You could start by finishing the second sentence here: "In Shakespeare's classic tragedy Macbeth, blood will always tell. Specifically, if we follow the motif of blood throughout the play, we can see that it means___."