Which three colors in the dictionary do not rhyme with anything?

There are only actually two colours that don't have any perfect rhymes, these are orange and silver. People believe purple to not rhyme with anything, but in fact there are two that do - hirple and curple, both of which I believe are in the English Dictionary. You will find assonances for orange and silver, for example orange can be loosely rhymed with "lozenge" or "porridge", and silver with "slither".