Crap. I don't have Photoshop.
I pulled it out the file and attached it as a PNG file - that keeps the transparency and makes re-use easy-peasy, I hope.
Then no confusion would be possible, and the colour of the promotions wouldn't really matter anyway.
Ah, I see. Though I have to say I'd miss the ability to further customise units through promotions, especially after the last promo of the line is received - but let's keep this thread about the graphics.
So unless you could write a guide similar to the tech/fac button creation guide, one which works for a freely available program like GIMP, it is best not to start using another style for special ability buttons.
Hmmm... I could produce a photoshop template that could be used pretty easily, but I'm not experienced with GIMP. However, the template for this particular style is *very* similar to the standard promotion button - if you can create Civ4-style promotion buttons, I could supply you with the background and give you the colour values for the raised part - that should result in near identical buttons.
I've put it on the to-do list, but I probably won't get to it for a long time.
Okay, nice to hear... do you take bribes?
If so, here is one (joking, labels are very minor, focus on important issues): I adapted Deliverator's spice resource (with his permission, of course) and created a trench feature.
It has some issues - the edge looks harder than the old trench, but I cannot change that without getting a lot of flickering between the tiles. It can sometimes look a bit cut-off close to land, but I cannot change that without moving it closer to the surface, in which case submarines/carriers completely vanish below the texture if they fortify.
Apart from that, it looks very similar to the current trenches, though a little bit darker. If you use it on a transition between shelf and ocean, put it on the ocean tile, not on the shelf tile, it usually looks better that way.
Included the XML-code and a button as well.
Cheers, LT.