Difference in hue between arterial (brighter) and venous (darker) blood!! 🩸💉 The upper 2 syringes are containing dark red blood drawn from a vein, while the bottom 3 syringes contain more reddish and brighter blood taken from an arterial source. Arterial blood is the oxygenated blood, bright red in color, while venous blood is deoxygenated, dark red in color (but looks purple through the translucent skin).