Two pats were served

'A large number of women at a luncheon were asked whether they could tell the difference between butter and margarine. Over 90 percent said they preferred butter because margarine tasted oily, greasy, and more like shortening than butter. Two pats were served, one yellow (margarine) and one white (butter). The ladies were asked whether they could discern any differences. The yellow pat (margarine) tasted like butter, claimed 99 percent of luncheon guests, but the white pat (butter) tasted oily like margarine.'

'Cheskin, L, Color Guide for the Marketing Medic, 1954, quoted by J.L. Zaichkowsky in The Psychology Behind Trademark Infringement and Counterfeiting, 2006.