In the framework-res.apk, check out the files starting with "progress" in res/drawable-hdpi. I believe those pngs are used for both the volume bars and any progress bars (like for downloads). I know they control the latter, but I believe they also control what you're referring to. Worth a shot either way.
Hboot 2.02 S-Off
Amon Ra recovery
More stuff that I'm too lazy to figure out and type.
MIUI 2.3.2_b1 ES (by Swiperat)
Extended Settings Mod
Tiamat 4.1.0 SBC
My wallpaper collection
If you think I can help you with something or need me to elaborate on a post then feel free to pm me. I'll try my best to help you out.
Oh, and I have a vagina. Fear me :P