呵呵，这个您肯定不对了

来自Wikipedia：

When carbon dioxide binds to hemoglobin, carbaminohemoglobin is formed, 。。。。。 Carbaminohemoglobin has a distinctive blue color that may contribute to the dark red color of deoxygenated venous blood (compared to bright, saturated red of oxygenated arterial blood), blue color of veins and the purplish or bluish color of tissues in hypoxia.