Rainbow adjectives are listed in this post. Each word below can often be found in front of the noun rainbow in the same sentence. This reference page can help answer the question what are some adjectives commonly used for describing RAINBOW.
awful, beautiful, big, bright
brilliant, circular, colored, colorful
double, first, glorious, great
large, little, lovely, lunar
magnificent, own, perfect, same
small, vivid, whole
Hope this word list had the adjective used with rainbow you were looking for. Additional describing words / adjectives that describe / adjectives of various nouns can be found in the other pages on this website.
Colourful
Amazing
colorful
Pretty
Dazzling
Radiant