Yellow is one of three primary colors, which means that it is one color only and cannot be made by mixing other colors. The shade of yellow may be lightened or darkened by adding additional colors, however. White can be added to yellow to make a paler shade, and adding orange or red will create a darker yellow.
The three primary colors on the color wheel are yellow, red and blue. All other colors can be made up of a combination of these three. Yellow can be combined with red to make orange, and green is made by mixing yellow with blue.