Don't know if anyone is still looking for this MOD? But I've worked out how to do it at last!!!!!
I've attached a link to a zip file that contains four different files. One for Blue, White, Yellow and Green. Just grab the file that corresponds to the colour you want then rename to SystemUI.apk.
The files are from the latest version (1.6.24). I wouldn't risk installing this on any other version.
Just for anyone who looks at this thread in the future, miui has since moved onto using a .9.png in the systemui.apk to show the top battery bar. This means that theme packs can now include changes to its color.