Purple is the color of the expansion symbol of the timeshifted cards in Time Spiral. Because they appeared in a rarity significantly different from any other rarity, they were assigned their own new rarity level (higher than rare).
Ever since a prank article in the InQuest #22 (February 1997) which featured purple cards (see Gallery), purple has been speculated to be the unreleased sixth color of Magic.
For Planar Chaos R&D actually playtested purple as a sixth color in the color pie , to convey the alternate reality of the set. A purple version of Mana Drain was planned and the basic land would've been either City or Cave. 
- ↑ Mark Rosewater. (September 25, 2006.) “Purple Reign”, magicthegathering.com, Wizards of the Coast.
- ↑ Mark Rosewater. (July 30, 2014.) "What color were you thinking of adding in Planar Chaos?", Blogatog, Tumblr.
- ↑ Paul Sottosanti. (January 29, 2007.) “The Color Purple”, magicthegathering.com, Wizards of the Coast.
- ↑ Mark Rosewater. (July 30, 2014.) "Can you tell us anything of what purple would have been able to do?", Blogatog, Tumblr.
- ↑ Mark Rosewater. (July 31, 2014.) "What would the basic land for purple be?", Blogatog, Tumblr.