The process of creating starfields in Photoshop might sound daunting considering how many dots are in a typical image. The task is really quite simple and not as time consuming as you might think. To start, select white and a 100% hard brush set at 3 pixels, and start placing random dots in the center of the canvas in a new layer named stars on a black background (separate layer). Do perhaps a hundred 3 pixel dots, then do 75 4 pixel dots, 50 5 pixel, 40 6 pixel, and work your way up to perhaps 10 pixels. Larger stars will be added at a later date. Duplicate the layer and move it, perhaps rotating it in the process. Merge the layers and duplicate again. Repeat until you are satisfied with the density of white stars. Duplicate once again and go to blending modes and add yellow. Adjust the opacity to 10 to 20%. Be sure to move and rotate the layer so it doesn’t cover the white stars. Duplicate the white star field once again and add blue. Same process except rotate the opposite direction. You may also want some red. Since you want more white stars than colored stars, you may want to duplicate your white stars are few more times, but be careful or you’ll soon have too many. You can always check to see the percentages of color stars versus white stars by Googling, although I’ve never found specific percentages. It doesn’t hurt to study images from Hubble and other sources.
There are many ways to approach this and they probably all work. The advantage will be that your star field will be separate from the background. If you don’t merge your colored layers, they can be turned on or off. Always save your PSD file without flattening it. Once you create a library of object, you can build infinite worlds.