Blood red Blood red The color blood red is a dark shade of the color red meant to resemble the color of human blood (which is composed of oxygenated red erythrocytes, white leukocytes, and yellow blood plasma). It is the iron in hemoglobin specifically that gives blood its red color. The actual color ranges from crimson to a dark brown-blood depending on how oxygenated the blood is, and may have a slightly orange hue. Deoxygenated blood, which circulates closer to the body's surface and which is therefore generally more likely to be seen than oxygenated blood, issues from bodily veins in a
White blood cell ways. Two pairs of broadest categories classify them either by structure (granulocytes or agranulocytes) or by cell lineage (myeloid cells or lymphoid cells). These broadest categories can be further divided into the five main types: neutrophils, eosinophils (acidophiles), basophils, lymphocytes, and monocytes. These types are distinguished by their physical and functional characteristics. Monocytes and neutrophils are phagocytic. Further subtypes can be classified; for example, among lymphocytes, there are B cells, T cells, and NK cells. The number of leukocytes in the blood is often an indicator of disease, and thus the "white blood cell count" is an important subset of