Persian blue is a slightly purplish medium-blue based on the color of the mineral lapis lazuli. This is related to the color ultramarine, that is the historical name for a pigment made from crushed lapis lazuli. The name Persian blue refers to the fact that the Middle East, namely Afghanistan, was historically the largest producer of lapis lazuli. This was imported to Europe since antiquity. In the middle ages, ultramarine was the most expensive pigment used in Europe such that the color became associated with institutions with high social status such as royal houses. The following palette includes Persian blue and a few related colors.
Deep Lapis Lazulii
Persian Blue #2
Ultramarine means "beyond the sea" and also refers to the Persian source of lapis lazuli. The actual color of lapis lazuli can be seen here: