Modio Tutorial
Well any way onto the tutorial
1.) Change all your armor colors to white (Primary, Secondary, and Detail)
2.) Put your profile onto your USB memory stick
3.) Extract your profile onto your desktop with a USB Explorer program
4.) Open it up in Modio and click "Edit Profile" under your gamer picture
5.) Open the file in there that says 4D5307E6 (Your Halo 3 profile)
6.) Search in the search bar in the bottom right corner of Modio. Search 02 00 00 00 02 00 00 00 02 under HEX
7.) When you find them change all 02 to 1E (Ultra Bright white)
8.) Rehash and resign your profile
9.) Replace the profile on your desktop with the one in the USB Xplorer and put the USB back into your Xbox 360
10.) Finally go on Halo 3 and gloat about your shiny new armor (Color)

Hex Editor Tutorial:
1.) Drag and drop your profile into the hex editor
2.) Search the Hex Code for 02 00 00 00 02 00 00 00 02
3.) Once found change all the 02 to 1E
4.) When done with that save it and replace the profile in the storage device
5.) Put the device back into your Xbox 360 and play Halo 3
6.) Gloat about your new Sexy shiney armor!

You NEED Horizon Diamond for there credit adder since it sets checks that Halo Reach does to make sure your account wasn't modded.

1.) Drag your profile or Halo Rach GPD (4D53085B) into Hex Editor and search your Halo Reach service tag in Unicode String.

2.) Above the service tag is your Primary Color, Secondary Color, Primary Emblem, Secondary Emblem, Emblem Colors, Emblem Background, and obviously your service tag.

3.) Look in the list below for you armor color and when you find it replace your current armor color hex with 1F which is Ultra Bright White.

4.) So lets say I have both my armor colors set to white I look for hex code like this > 02 00 00 00 02. Then I change them so I have Ultra Bright White on. It will look like this > 1F 00 00 00 1F.

5.) Drag your account into Horizon then open up Halo Reach Credit adder. (Add 1,000 Credits if you want). Then click save.

6.) Put your account back on your USB and enjoy that nice shiny armor.

00 = Steel
01 = Silver
02 = White
03 = Brown
04 = Tan
05 = Khaki
06 = Sage
07 = Olive
08 = Drab
09 = Forest
0A = Green
0B = Sea Foam
0C = Teal
0D = Aqua
0E = Cyan
0F = Blue
10 = Cobalt
11 = Ice
12 = Violet
13 = Orchid
14 = Lavender
15 = Maroon
16 = Brick
17 = Rose
18 = Rust
19 = Coral
1A = Peach
1B = Gold
1C = Yellow
1d = Pale
1F = Ultra Bright White