When you use the letters & numbers, it's called a 'hex' code. It's called that because there are 6 of them.

Here's a page with some explanation and codes for some colors. I kind of like tomato and turquoise. If course, I see that typing the words tomato and turquoise works too. There's crimson, and springgreen, and aquamarine, coral, cornflowerblue... you could go crazy!