Program: Photoshop 5.0+

1. Press D to reset your colors. Create a new 300x300 RBG image.

2. Go to Filter -> Render -> Clouds.

3. Go to Filter -> Brush Strokes -> Ink Outlines. Settings:

Stroke Length: 5
Dark Intensity: 20
Light Intensity: 10

4. Go to Filter -> Blur -> Motion Blur. Settings:

Angle: 0
Distance: 725

5. Now use the Rectangular Marquee Tool and cntrl+U to color it.

You will get something like this: