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.
Primary lymphatic organs are where lymphocytes are formed and mature. They provide an environment for stem cells to divide and mature into B- and T- cells: There are two primary lymphatic organs: the red bone marrow and the thymus gland.