The Meaning of Life, the Universe, and Everything.
This is a structure file. Place it into your world's structure folder and it will load a command block with two § signs. Build your /summon or /entitydata command around them, put one hexadecimal number from the list behind the § (which might be invisible sometimes) to color the text behind them. For example:
No names of entities and names of items cannot be coloured.
This is 100% incorrect. Not only can they be colored, they can be colored in-game without needing any kind of external tools. There are several ways to color mob and item names.
Firstly you can go with the easiest way: teams. Create a scoreboard team and set its color to any color, then put the mob on the team. it's name will now be the color of the team.
The second way, and the best way, is to use the section symbol §. The section symbol is used to format text in Minecraft, but you cannot paste the character in-game. There is more than one way to get it though:
json sign exploit
using structure files
To get them using MCEdit or NBTExplorer you need to physically leave your world and/or close your server and requires you to have access to your servers files (if you are on a server, of course). MCEdit requires you to leave the world, open the world in MCEdit, navigate to the command block and edit the command to add the formatting. Similarly NBTExplorer also requires you to leave the world. The easiest way to do it with NBTExplorer is to CTRL+PickBlock the command block so it's in your inventory with the command still in it, then use the player.dat file to edit the command block command. Structure files are slightly harder to use when making the formatted command but once you make it, you can use structure files to move it around worlds easily. The reason it is hard is because structure files are written in the NBT format, so unless you know how to work with that format (decoding and writing in it) it will be a bit hard.
The json sign exploit is by far the easiest way. It does not require you to leave your world to work and can be made in a matter of seconds. In short you make a json sign that has a clickEvent, which does a blockdata command or setblock command to get a command block with the section symbol in it using an exploit in the way it reads unicode. I go over this exploit here in this video:
You could also use this online generator http://mctoolbox.me/colors/ which makes the json signs for you, again you do not need to leave your world to use this method.