Why are blood cells are red?

Answer 1

Red blood cells contain hemoglobin, an iron-containing molecule that binds oxygen. As with rust, the iron compounds turn brighter red when the hemoglobin absorbs oxygen.
The blood in your veins are blue. Red blood is red because the color of oxyhemoglobin is red because there is iron in oxyhemoglobin, causing that blood red color.
Red blood cells are red because the iron in the heme group of the four hemoglobin proteins react with oxygen (think what color rust is) to produce a red color.

Answer 2

because they contain a protein chemical called hemoglobin which is bright red in color. The blood is red because of hemoglobin, hemoglobin on the other hand is combined with oxygen that gives blood its red color. Hemoglobin is a protein substance which contains iron.

Answer 3

They are red because they are filled wth oxygen and hemogoblin