A secondary color is a color that is created by mixing two primary colors in equal amounts. The primary colors are red, blue, and yellow. Therefore, in order to determine which of the given options is a secondary color, we need to know which two primary colors were mixed together to create it. Out of the options given, blue and red are primary colors, while green and orange are secondary colors. Green is created by mixing blue and yellow in equal amounts, while orange is created by mixing red and yellow in equal amounts. Therefore, the answer is: green and orange are secondary colors.