If you plan on using a major API for your graphics, you can look at using the alpha channel (some libraries or component suites support it others don't). In some graphics modes you have RGBA or ARGB, etc... this will take that 4th byte(in a 32bit color mode) of video data and use it to do the alpha blending on that pixel. Could this be what you are sugesting aswell? Keep in mind that this is relatively harder to produce since your sprite or torch image will be seen and possibly only stored in RGB format.