This guide shows you how to get multiple hud/pipboy colours.
Credits to ShimaHonnou/youtubeuser/ he provided me this info

Find FalloutPrefs.ini, open it using Notepad.
if your using XP Go to Windowsdrive \Documents and Settings\yourname\My Documents\My Games\Fallout3
if your using Vista or above Go to documents/mygames/fallout3/falloutprefs.ini

REMEMBER TO MAKE A BACKUP

These are near the bottom.
uPipboyColor=
uHUDColor=

Pip controls the PIPboy, and HUD, well, controls the HUD color.

Just plug one of these values in. After you do, just don't touch the Pip or HUD color in the ingame menus and you'll be fine.

4290134783 - Default Amber
2552000000 - Magenta
2551000000 - Magenta2
2552552552 - Deep Purple
2559990000 - Tan
2549990000 - Faded Green
2551000000 - RED OMG RED! /Kinda slightly purple
0002550000 - Pure Blue
2550010000 - Radioactive Green
2550100000 - Faded Radioactive Green

0000000000 - Default Greenish
1000000000 - IceyBlue
2000000000 - Light Purple
3000000000 - Yellow Green
4000000000 - Pure Orange
5000000000 - Blue with a Touch of Purple
6000000000 - Crysis Icey White
7000000000 - Deep Pink
8000000000 - Gold
9000000000 - Deep Green
0100000000 - Deep Cyan
0200000000 - Green-esque Cyan
0300000000 - More Green-esque Cyan
0400000000 - Even more Green-esque Cyan
0500000000 - Wtf Even more Green-esque Cyan
0600000000 - Holy poo even more Green-esque Cyan
0700000000 - Alright Its Green now, not even Green-esque Almost Pure Green
0800000000 - Pure Green
0900000000 - Deep Ice Blue
0010000000 - Dark Ice Blue
0020000000 - Where did it go? Dark Ice Blue
0030000000 - Deep Ice Blue

7050000000 - Deep Pink
7020000000 - Lavender
7900000000 - Tan again
7990000000 - Deep Pink /Slightly darker
7999000000 - Pure Goldenrod
7999900000 - Red Tinted White?
7999990000 - Pure Yellow
7999999000 - Faded Yellow
7999999900 - Still Faded Yellow
7999999990 - SLIGHTLY more Faded Yellow
7999999999 - Even more Faded Yellow

705032704 - This is blue
Remember to save your notepad and make a backup
Hope this helps , again Credits to ShimaHonnou/YTusername