red blood cells & white blood cells

When a lower oxygen concentration is inspired than normal, the colour
of the red blood cells are bluish colour due to decrease in the affinity of
haemoglobin to oxygen due to cells asphyxia. Medically, this situation
is called cyanosis.

The number of white blood cells will increase if a man is infected by
harmful bacteria. The white blood cells increase their number in order
to fight against the bacteria and win the battle.