This is one of over 4720 effects generated by Filter Forge, a Photoshop plugin that allows you to create your own filters.
To open this filter, you must have Filter Forge 1.0 or higher installed on your computer. If you don't have it installed yet, click here to download Filter Forge
This filter applies colored cow spots to one color in your image. To use, select the color you'd like to apply spots to with the "Color to Cowify" setting. Then, select the color for your spots. You'll probably need to adjust the three tolerance values to get good, clean coverage of your colored area. (Or you may wish to leave it grainy, for grungy or stenciled effects.)
cow spots stencil