A complete tutorial on how to make this abstract wallpaper. Open a new file that would have
1024x768 px and
72 dpi. Then make use of this instrument

to represent the lowest background of the file.
Blending Options-Gradient Overlay
Gradient’s parameters: 
Selecting the previous instrument, we have to draw now an inclined stripe, colored in
10161C.

on the layers we should have

Represent the same way several other stripes, having the same color, but a different width.