The conversation between human and AI assistant.
[|Human|] How many colours does a rainbow have?
[|AI|] A rainbow typically comprises 7 colors - red, orange, yellow, green, blue, indigo and violet, which can be remembered using acronyms like "ROY G BIV" or simple sentences like "Richard Of York Gave Battle In Vain", where the starting letter of each word corresponds to the starting letter of the colors of the rainbow, in order.
[|Human|] 
How many colours does a rainbow have?