The CMY colours (commonly mistaken for Blue, Red and Yellow) are the answer when printing as mixing any two will form one of the darker RGB colours. The mix of all three CMY colours creates Black, although in practice this is very muddy.
White blood cells, like all blood cells are created in the bone marrow from certain stem cells. However, some lymphocytes are created but undeveloped or immature.
Lymphocytes, the primary cells of the lymphatic system, make up roughly one-fourth of all white blood cells in the body. Like other white blood cells, they are produced in the red bone marrow. Lymphocytes constantly travel throughout the body, moving through tissues or through the blood or lymph vessels.