Two people never see the same rainbow.

This one requires some explaining. When Isaac Newton redefined what color and light really are in his experiments with light refraction, a new wealth of information was found. 

What is most known today is that the normal light we see is a combination of every color of light. You may know that rainbows occur when light is refracted from the moisture in the air (most often following the rain). 

Like in Newton’s original experiment with refracting light using a prism, each particle in the sky serves as a prism to refract light, giving us the whole color spectrum. 

There is a series of rules that have to come into play for a rainbow to occur at all, but what’s most interesting is that only one color is visible from any one particle at a time. 

As you change the angle you’re viewing the rainbow from, you see the color change. That means whenever a rainbow is visible, no two people can see it the exact same way. 

(Source)