Remember we learned before about measuring waves using
wavelength.

(from: wikipedia
sine)
And we learned that how often something happens in a given amount of time is called a
frequency.

(from: wikipedia -
frequency)
Well did you know that the colors of the rainbow are all different because of their
wavelength and
frequency?
For example, the color red has a very long
wavelength, and a very low
frequency.
But the color violet has a very short
wavelength, and a very high
frequency.
That's why the colors of the rainbow are in the order they are,
and why we put them in the order of
ROY G BIV.
Red is the longest
wavelength and lowest
frequency.
Violet is the shortest
wavelength and highest
frequency.
Green is right in the middle.
Sometimes it's easier to understand by looking,
so here's a good picture that helps show how the different colors have different
wavelengths and frequencies: