A viewer sees a spectrum of colors coming from a faraway raindrop. This is due to a phenomenon called dispersion, which happens when light passes through a medium like water.

Here's how it works:

* White sunlight is actually a mixture of all colors of the rainbow.

* When sunlight enters a raindrop, it is refracted (bent). Different colors of light bend at slightly different angles because they have different wavelengths.

* This separation of colors causes the spectrum to be visible. You see the red light bent the least and the violet light bent the most.

So, you don't see a single color, but rather a beautiful rainbow of colors when you look at a distant raindrop.