I guess I was trying to find a way to partially eliminate the game's builtin alpha effect for the sights, even with the slider at the default 100% the reticule gets really washed out against light backgrounds (goes almost white). I'm trying to nail the right colour for the reticule.
btw trial and error with the sights is a PITA - change the colour, restroke the paths, reapply blur, flatten the image, save as BMP, open in Paint to convert to 256 BMP, back to AH, spawn on runway, taxi to a hangar to check the builtin alpha effect.
just got a Intel mac so my (very) old PPC photoshop doesnt work on it. never really used Gimp before, its very impressive for a GPL app but missing some of the real timesavers from PS (primitives paths, layer effects, 256 BMP export etc.)