If you can get your hands on a syringe, there's an easy way to find
out. Seal some blood in a vial, pop it into a hot water bath, and
observe the changes.
If you don't have a syringe, you can still try it with oxyhemoglobin
(which is, I believe, the red you're asking about anyway).
Unlike your wine and butter posts, I'm actually interested in the
results of this, so please post them once you've done it.