You need the Image Mod.
http://imagemod.spaceempires.net/ . I believe that the readme and the game website's download page specifies this.
The colony module has a special mount only available to the 330 kT colony ship that makes it 30 kT. The colony ship was originally 3300 kT, but that cause the Artificial Idioit to think that they were equivalent to very large warships due to the simplicity of the score system.
So now they are only 330 kT, and require the colony module to be mounted.
Just select the colony ship, then click on the Mounts button.