To make colored text in a book, first you need to copy/paste this symbol into a book and quill: § . when you put it in a book, it will be white and it will look different. After you put it in the book, type one of these numbers/letters in the book after the symbol (no space):

0 - Black (normal)
1 - Dark Blue
2 - Dark Green
3 - Dark Cyan (the color of "cyan" wool)
4 - Dark Red
5 - Dark Magenta
6 - Gold
7 - Light Gray
8 - Dark Gray
9 - Purpleish-Grayish-Blueish
a - Light Green
b - Cyan (real cyan)
c - Light Red
d - Light Magenta
e - Yellow
f - White

You can also change other stuff:

k - Randomly changing letters
l - Bold
m - Crossed out
n - Underlined
o - Italic (slanted)
r - Normal

everything after the §(letter/number) will be the color/font that it says, to get it back to normal font, use §r.

Example: If you wanted to say: "12Me21 is AWESOME" you would type: 12Me21 is §l§4A§6W§eE§aS§2O§9M§1E

You can also do this on signs, but since you can't copy/paste text into signs, you need to use mods or MCEdit to make colored signs.