A Look at Monster Book

Hmm hope this is the best place to ask my question...

What does the different colours of monsters name mean? Why are some white, yellow or red?

Heh, nothing to do with monster book, but here's the answer...

Yellow: This monster is very weak for your level. Around 10 levels below yours.
White: Not yellow or red :p Simply close to your level.
Red: Too powerful for your level. Around 10 levels above.

Not sure about the exact level difference that triggers it, but you get the idea.