So does Anyone know where I can find the original "full colour" versions of the water colour  portraits in the NPC folder? The ones for NPC's you only talk to and don't even have in your party. 

Are these even out there or does obsidian still have them all?

And does anyone have the skillset to reverse engineer a water colour portrait into a full companion one? 

 

Any help would be greatly appreciated. 

I doubt they exist. Obsidian used this style so that they could make more portraits easily. If they had to make the normal ones and them convert, it would actually be even more difficult.

There are no full color versions of watercolor portraits; full color portraits take several hours to make, watercolor portraits were a way to save up time. "Reverse engineering" a watercolor portrait into a full portrait would require changing the size, tracing the lines and basically painting it over.