Ok, so it will also be useful to know what your intended need is. By "dissolve", I assume you don't really mean "dissolve" in the chemical sense but "decompose", meaning to get rid of the pigment. The pigment in blood is heme, and a good way to destroy it is oxidation. Peroxide should do the job, but 3% is pretty weak and the reaction will be slow. This is why I suggest any number of other strong oxidants, including higher percentage of peroxide, nitric acid or bleach. Safe (stable) organic peroxides may also work. Do be careful with the stronger oxidizing agents, as they can be dangerous to handle.
One other thing. Some polymers may react with strong oxidants, so just keep this in mind. I don't know what kind of plastic you are using, but I suggest a spot test on a clean part of the surface before you try out any of the strong stuff, lest you remove half your plastic along with the blood.