This listing is for Axcel and Spothogg, not for Shrewd. By color: Blue, Purple, and White. The blue & purple LEDs work full-spectrum and are ideal for green and blue fibers. The UV LED works best when shining at fibers perpendicularly, commonly seen in hunting sights. The white LED is ideal for red and yellow fibers. 3/8-32 LED features a Water-Proof CNC T6 aluminum housing, with nylon-braided cable sealed by epoxy, covered by 5/64” thick tempered-glass.