In the 1960s, the flip-flop was a practical shoe worn by the working-class and was only made in a blue-and-white design. It became so associated with the poorer sector of society that it was listed as one of the fundamental goods by the Brazilian government, along with other household products. Traveling merchants sold them from the back of their vans. Variations in color and design are claimed to have all started serendipitously in 1969 when one batch of flip-flops came out to be green and suddenly gained popularity.