You will need:
-Black ops 3 (obviously)
-HxD editor (or any HEX code editor)
-Access to 'Create a Class'
1. Download HxD editor (link will not be provided but it's not hard to find)
2. Load up black ops 3, go to multiplayer, create a class, then hit rename.
3. Once in the rename screen, rename the class to what ever you want with 2 extra characters in the front of the name (for example, if i wanted my class to be called 'Custom Class' i'd rename the class to 'd7Custom Class').
3. Now, Open HxD go to tools, memory, then open Blackops3.exe.
4. Now press CTRL + F on your keyboard and search for your class name. (it will say it will take a few hours but it will only be a few seconds)
5. Next where you added your 2 extra characters at the start of your class name, replace the 1st one with a '^' (shift + 6) and a the second a number between 0 and 7 (9 is grey and 8 is default colour).
Colour codes are:
^1 = red
^2 = green
^3 = yellow
^4 = blue
^5 = light blue
^6 = purple
^7 = white
^9 = grey
^0 = black
6. Now press CTRL + F again and search for the class name again (d7Custom Class)
7. Now make the same changes as you did on the 1st edit (where you added your 2 extra characters at the start of your class name, replace the 1st one with a '^' (shift + 6) and a the second a number between 0 and 7) and then press save and tab back into black ops 3.
8. Done, now you will have a coloured class name. You can repeat this for all classes of your choice