Hmm, ok. I used to get Bright from SimmersPaintShop which I think is closed. I currently use Brighter, which is just Bright with a little GUI thingie to make it easier to use. Here, lemme zip up mine.
https://www.dropbox.com/s/24ws3sy5njrdgt7/Brighter.zip?dl=0Just unzip it and plop the folder anywhere you want. So what you do is first get your full color BMP, so export one out of the template or save the skin you are working on. Then run Brighter.exe.

This is the first screen, click browse and select the .bmp file you want to convert. If you have several, you can select one and then toggle "Work with multiple files" and it will convert all files of that type. Once you have the file(s) selected click next.

On the second screen I then click Advanced and then the Other tab, there I check Best under the Presets section.

Once done, click ok and you are back to the second screen and you hit Go. A little command prompt type screen will pop up as it does it's work, once it closes the process is done and you can close brighter. You should find the converted skin in the Brighter folder.
DW