I wish I could help Fran, but I've never tried the 3D Basics ver. of Carrara and I don't know if the mapping/shader functions are the same as in Carrara Standard/Pro. I have had no problems in importing Wings-built models and texturing them in Carrara. Wings is still my preferred modeler. 
   I usually just run my Wings models through UVMapper standard and save out the UV mapped mesh object. When I bring it into Carrara all my material groups arrive as the default gray material. If I want to use simple colors as you describe, it is a simple matter to select each separate material group and then go to the texture room and use the color picker in the color channel to assign a simple color. Sorry I'm not at my home computer right now or I'd post some screenshots for clarification.