A solution made by dissolving or infusing a drug in alcohol and water; by extension it refers to a trace of something, a dye or pigment, the essence of a colour–a hint or a tinge of it that can be used say to turn white into pink by adding red, or blue into red to make purple.
It also specifically refers to the colours used in Heraldry, which were made and used in very specific ways and categorised into light tinctures, known as metals, and dark tinctures, known as colours.