Exactly what version of TEC are you using?
Purple area's mean you are either physically missing required textures, or the *.esm/*.esp you are trying to use, refers to non-existing textures. I.e. you are using the wrong *.esm/*.esp.
Reinstall the package for the non-Cobl enabled version. Did you also install all of the files from the Resourcepack?
Does that work? Perfect, now you have a working environment!
Then, if you still want to use Cobl, install the Cobl-enabled version of TEC and see that you meet all requirements for the use of Cobl.
Some more info:
I got this info when communicating with the expander of the mod, when preparing to install Cobl myself, to get Cobl-things working:
For installing cobl...
I would recommend to start with the basics and to install the optional cosmetic pack maybe later on ( I personally don't use it)
and to use the following files :
the cobl main esm (the resource esm which contains all the resources) is required !!
the cobl glue esp (this esp adds the the cobl items into the game...like adding books to vendors etc)
the cobl tweaks esp (tweaks creatures and npc's to use cobl items)
salmo the baker esp (Salmo the baker is selling a lot of new amazing food in skingrad...as well he is delivering skingrad castle..and different shops and taverns..amazing mod

)
for the cobl resources :
just copy the meshes, textures and sounds to your oblivion data folder and let overwrite if asked...
for playing Tec cobl you need the cobl esp of the mod ..simply dl the cobl version and replace your current esp with the cobl one
and you need the cobl main esm....that's it
hope this helps