The color wheel is made up of three different types of colors - Primary, Secondary, and Tertiary. The primary colors are red, yellow, and blue. They are called primary for a couple of reasons. First, no two colors can be mixed to create a primary color.
RNA contains uracil and DNA Thymine. RNA has five bases, but DNA only four. DNA contains a deoxyribose sugar, but RNA contains ribose sugar. DNA is a double strand of nucleotides, but RNA a single strand.
The different chemical structure of each base leads to a different orientation of polarity of the molecule. Thus, only Thymine (or Uracil) can form an H-bond with Adenine, because it is the only base complementary to the shape of Adenine. The same applies for the Cytosine-Guanine bond. You may find those images useful: http://www.exodus2006.com/lyuben/Genesis... http://www.uq.edu.au/vdu/DNA%20nitrogeno...