Posted By: wraggster
David Hawley has posted a ton of info of how to edit your Mii, heres an excerpt:
Nintendo This should try to explain how Mii's with different coloured pants can be created through an explanation of the Mii ID.
Before we start you need to understand how to change the Mii ID. The basic format of the Mii ID is a hexadecimal in the form xx-xx-xx-xx. This is easily edited with any Hex editor, I used HxD.
If you don't know how the binaries are formatted the Mii Data Specification is very helpful.
Quick Mii ID guide
0x00000000 - 0x1FFFFFFF Creates Special Mii - Gold Pants
0x20000000 - 0x3FFFFFFF Creates Normal Mii - Black Pants
0x40000000 - 0x5FFFFFFF Creates Special Mii - Gold Pants
0x60000000 - 0xBFFFFFFF Creates Normal Mii - Black Pants
0xC0000000 - 0xDFFFFFFF Creates Foreign Mii - Blue Pants (uneditable)
0xE0000000 - 0xFFFFFFFF Creates Normal Mii - Black Pants
More Info --> http://www.davidhawley.co.uk/blog.aspx