The Indigo skin for the MAC-10 was added in the Operation Hydra case released on May 23, 2017.
The Indigo skin features a blue, purple and pink tie dye pattern over the whole weapon. It has a marbled, swirling look reminiscent of the psychedelic art style of the 1960s.
The Indigo is a relatively common MAC-10 skin from a retired case. It has average popularity and market demand.