CKEditor is one of the most sophisticated webbrowser base html editors available.
The original version was named fckeditor and going to version 3 it was renamed to be simply ckeditor.
The F in the name was for the first name of the author, Frederico.
When you use the version 4 of the editor, you will receive a new look, due to large changes in the default skin. It is now blackgray/white instead of the "colorful" 3.x version.
A huge improvement in my opinion. The bright colors in 3.x where not looking very professional.
If for some reasons you wish to use another skin, then you can download alternate skins from the ckeditor home page with this link.
When downloading, it tells you how to install and activate the new skin.
Unfortunally this info is mostly wrong, and even in the main documentation the same errors are present.
To successfully install the new skin, you have to put the extracted files in the skins subdirectory (not in the plugins).
And to activate the new skin, you have to specify the config.skin = "new_skin" property. (And not the config.extraPlugin as documented).
So if you wish to have the "old" 3.x icons and colors, you can download the "kama" skin and activate it.