how do i make this :

Well for me I use this tutorial
- http://www.good-tutorials.com/track/4439
and i use the bucket tool to fill in the 2 colors but i know theres an easier way but i don't know it

i think that's the only way.

Use the polygon lasso tool to make rectangles. Press shift to make it exactly at a 45 degree angle. When you make the shape, fill it in. It's easier this way because you don't have to use the pencil tool if you want a thick line. Which reminds me, you can use the line tool. =)