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.
thymine has a methyl group which is not found in uracil. Having a methyl group means it is more stable. That is why thymine is more stable that uracil. DNA is more stable than RNA because DNA has deoxyribose sugar and RNA has ribose sugar. So DNA has thymine base and RNA has uracil. Also, all genetic info is stored in DNA, so DNA has to be stable and 'long-lived' to stored the information.