The slide above is that of normal blood.  Most of the cells are red blood cells.  Those with a purple stain are white blood cells.  The small purple specks are platelets.  Red blood cells have a biconcave shape.  This is the reason they appear white in the center.

The large purple cell on the left, above, is a lymphocyte.  Lymphocytes are important in the body's defense.  They recognize antigens and produce antibodies and destroy cells that could result in damage.

The large purple cell above, is a monocyte.  both lymphocytes and monocytes are agranular leukocytes.  Monocytes fight bacteria, viruses, and fungi.  The are the biggest type of white blood cell.  They are formed in the bone marrow.