not sure how to change it with color.properties, but there's a workaround. make some new images in the particles folder, name them stuff life breath1.png, breath2.png, etc, or whatever you want to name them. then change dragon_breath.json to reference these new files. if you're using optifine, it will use those new particles, so you can adjust the textures to cancel out the baked-in coloration (eg. making them green would result in gray particles).