Examples found on ebay. Yellow bottoms.
Most cup bottoms were yellow, although some blue have been seen. Note the two-handled creamer cup.
The "Fairy Tale Set" had a smaller serving tray (5" x 7"). It came with three regular size plates, three blue saucers, and three yellow cups. SRP $1.29.
Box images via toysandmorect.
Photos of two sets are shown on page 6 of the 1967 Snow White theatrical re-release Merchandise Supplement which was included with the pressbook.
It's probable that other sets were also produced by J. Chein & Co., which may explain the blue-bottom pieces and the two-handled creamer cups.