Here the word opposite refers to the placement of colors opposite each other on the color wheel. Along with the Red/Green combination of opposites, Orange/Blue and Yellow/Purple are also totally opposite colors. The other aspect of being called opposites is that they share NO common colors. For instance with Red and Green: Green is made of yellow and blue and a pure red has no yellow or blue or green in it. The same is true of Yellow and Purple or Violet. Yellow contains no red, blue or purple. They are thus opposites. Again, as the primary and secondary colors appear on the commercially available color wheel these colors are positioned opposite each other. Primary colors (red, yellow, blue) and their opposites (green, purple, orange - also called the secondary colors) are denoted as complementary colors because of their relationship as opposites.