My 1991 Platform 5 Combined Volume lists all the extant Mark 2d TSOTs at that time as wearing Intercity livery: 6600/01, 03-05, 07-09, 13/14, 16-19.
For additional information, prior to this, my Ian Allan 1987 Coaching Stock book lists 6600 and 16 in Intercity livery, and 6601/04/05, 13/14/19...