198 Bright Reddish Lilac / Light Purple
BrickLink: Light Purple
Introduced in 2004 with Duplo Dora the Explorer sets. One of the few Quatro brick colors, and the color of the fleshie Dumbledore minifig.
It looks as if this 2x2 brick never appeared in sets, but I think they came from Pick-a-Brick back in 2007 or so.