Like most commercial Lavender mixes, Daniel Smith’s Lavender is a mix of Titanium White (PW6), Ultramarine Violet (PV15), and Ultramarine Blue (PB29). This is a convenience mix; you can mix it yourself if you have the components, although my personal mix didn’t granulate as much as DS’s premixed one.
Lavender can be used as a sky color on its own or as a component in a bright/light sky blue (for example, with Phthalo Blue or Phthalo Turquoise). I can also imagine it being a convenient mix for hazy, distant mountains, flowers, snow, and shadows.