Guide to making this sort of texture
Made using photoshop CS4
Difficulty - easy
should be translatable for programs that have layer blending modes and blurring filters, except the last, optional step
This guide is for people just starting out, so there's information for where to find things.
1. Open a new document. The size you choose depends on how large of a texture you plan to create. Mine was 300 x 300
2. Fill the background layer with the color black, using the bucket tool (2).
3. Add a new, blank layer (4)
4. Click on the brush tool (1) then choose a round brush, with the hardness set at 0%, and the diameter set large enough to take up a good portion of the document. Make sure the foreground color (3) is set to white.
5. Draw a dot or squiggle on the blank layer. The reason for using a soft brush is that the softer, lower opacity, edges of the squiggle are the spots that will eventually take on the color. The bright white center will provide a glow. This kidney bean thing is what I ended up with.
6. Add a new layer, and use the brush to add some bright colored dots or streaks on top of the white brush marks.
7. Change the blend mode (5) of the color layer. Setting it to overlay will let the bright white spot from the lower layer shine through the color layer, and the soft edges of the white layer will blend with the colors and create a bright glowing ring. On soft light, it will create a similar, but softer effect. Screen will let more of the color show through, and brighten the colors. Picture 1 is the color layer on 'normal' - next is overlay, soft light and screen.
.:Duplicating the color layers can make the effect stronger. example, below shows overlay, soft light, and screen color layers duplicated three times.
Duplicate, and mix the layers on different settings until the effect looks the way you want it to.
8. Merge all the layers, except the black layer. In photoshop, turn off the visibility on the black layer (click the eye symbol) then choose Layer > Merge visible.
9. Turn the visibility of the black layer back on, then, blur the new, merged, color layer, by going to Filter > motion blur or gaussian blur.
10. Flatten the image by going to Layer > flatten image. The end, if you want it to be, but even after it's flattened, you can keep duplicating it it and setting the duplicates it to different blends to see the results. :)
For example the above is the preview image, that was duplicated once, with the copy set to soft light, to deepen the color, and allow more of the black background to come through.
The preview image at the top of the post was made with three overlay layers in a row, then three screen layers, all on 100% opacity, with a gaussian blur of 43 pixels. These sorts of textures are usually used on screen.
Other possibilities - blurring the initial white dot, before adding the color layer, or using the smudge tool (the finger across from the paint bucket in the first picture to smudge and swirl the final result. Another option is to go to Image >adjustments > variations, and use that panel to change the color of your blur texture, or lighten/darken it.