A single raindrop illuminated by sunshine doesn't actually "disperse" colors, but rather refracts them. This means it bends the light as it passes through the water droplet.

Here's how it works:

1. White sunlight is actually a mix of all colors of the rainbow.

2. When sunlight enters a raindrop, it slows down and bends (refracts) due to the change in medium (from air to water).

3. Different colors of light bend at slightly different angles. This is because each color has a different wavelength. Violet light bends the most, while red light bends the least.

4. The light then reflects off the back of the raindrop and bends again as it exits the water droplet.

5. Because of the double refraction and the shape of the raindrop, the colors are separated and we see them as a rainbow.

So, a single raindrop doesn't disperse colors, but rather acts like a tiny prism, refracting white sunlight into its component colors.