This is a rather silly question, but I was wondering how everyone was able to change the color of their usernames?

They didn't change them.

If you scroll down to the bottom of the Board Index, there's a key to the colors. I think blue is Editor, yellow is Marcher Lord (I think that's like a moderator?), and red is Admin. But you should look for yourself.

Ooooooh, okay! It's position then?

Yup!

but don't ask me what they mean - I don't know.

The Administrator is the site owner. Namely, Sir Emeth. The Editors correct grammar mistakes. Global Moderators make sure the forum is protected from spamers, malicious users, etc. Honor Role Moderators are kind of like Global Mods, but they've been appointed for being...honorable, might be the right word. Marcher Lords are users assigned with the duty of keeping the forum alive, promoting healthy conversation, etc.

Talk to Emeth. He knows way more than me!

Neat system! Now I know how it works.

Thanks for filling me in! I'm still learning the ropes, as you can see. XD