1. Open photoshop (I use CS2) and go to File/New.

2. Make a background of any dimension and use a color (a light hue is preferable).

3. Then go to Fliter/Texture/Texturizer/Stained Glass.

4. Here you will tweak Cell Size, Border Thickness and Light Intensity settings to your liking.

5. Press OK and then use the fill bucket and add colors within the borders of the cells. Voila!