Next to brown, purple appears to have been the most popular colour of the early 1970s. It predominates on the covers of at least one third of the pattern catalogues I own from that era. This example (another one of my acquisitions at "Love Vintage" fashion fair) dates from 1971.
However, purple didn't have quite the staying power of brown. By the end of 1972 purple appears to have been overthrown and large checks taken its place on the cover of the world's pattern magazines.