Roy G Biv is a memory aid used to recall the order of the colors of a rainbow or the rainbow pattern (spectrum) created when a prism breaks up white light by refracting different wavelengths (colors)...
Scientifically speaking.... rainbows are caused by refraction of light by water droplets (mist). This is why you can see rainbows after a rainfall or near a waterfall, because there is mist in the...
The fictional "Roy G. Biv" is the acronym mnemonic for the 7 colors of white light, in order of their wavelengths from shortest to longest :
Red, Orange, Yellow, Green, Blue, Indigo, Violet = ROYGBIV...