Slice0Pie

..... <--- feels like an idiot

Blood is always red. Deoxygenated blood is actually a darker shade of red than oxygenated blood. Doctors know this because they can draw deoxygenated blood into a vacuum-sealed pouch.

The red vs blue debate is a long-standing misconception, because there are veins and blood vessels in your skin that are colored blue, leading to the mistaken impression that deoxygenated blood is blue.

Bifrost is correct. Human blood exists in shades of red, depending on oxygen content. It might interest you to know that some animals, notably the horseshoe crab, use hemocyanin instead of hemoglobin to bind oxygen, resulting in blue blood.