4f92ee <--- let's break this down.

1. Break it into 3 chunks, so (4f, 92, ee)
2. Those chunks represent (Red, Green, Blue)
3. Those 2-digit chunks are numbers and letters that represent a value between 1 and 256.
4. Each digit uses the number 1-10, and then a-f, in order to have a 16-base value, and 16 * 16 is 256.
5. So 4f would be a darkish red, mixed with 92, a lightish green, and ee would be a very light blue.
6. Mixed all those values toether to get whatever that color is.
7. It is exactly like using rgb(45, 150, 240) in css. (These are made-up numbers, I don't know wha t#4f92ee corresponds to), but more concise.

Try this article.

Guil also explained everything here: https://teamtreehouse.com/library/color-values-3

Hope that helps!