As FM14 now has players with colourful boots on. This is now a Download for FM13
Download the file
http://www.mediafire.com/download/gza466l4ql59ds7/Boots.rarChoose which boots you would like to use in the game.
Save your FM game and close it.
First I would rename the old files in each of the folders below to oldboots.png and oldboots.dds in case you decide to use the default ones again.
Then copy boots.png and boots.dds from folder of boots you plan to use into the following folders. You can pick three different boots if you prefer (one for Players, one for GK's and one for Physios)
Players : C:\Program Files (x86)\Steam\SteamApps\common\Football Manager 2013\data\sigfx\players\outfield
Goalkeepers : C:\Program Files (x86)\Steam\SteamApps\common\Football Manager 2013\data\sigfx\players\goalkeeper
Physios : C:\Program Files (x86)\Steam\SteamApps\common\Football Manager 2013\data\sigfx\players\physio
Start up your FM again