Are you talking about the background? If so, it's very easy.
- Create a new project in Photoshop, with a nice height and a decent width to see your effect.
- Draw a vertical gradient from top to bottom with your favorite colors.
- Create a new layer
- Select the top half of the image
- Draw a vertical gradient with white, but with different opacities (eg: 75% to 100%)
- Crop the image to a width of 1, according you've made perfect vertical gradients.
- Save it and import it in your VS! (Look for tutorials to create MSStyles somewhere)