I can see where shimano are coming from with the new plastic. They needed some thing to compete with the durability of Z man type plastics and they have also gone down the biodegradable road, to cover all bases.
Due to the different materials used and process to make them, the colours were never going to be identical to the originals. As it is a whole new style of plastic, I can also see why they are a different shape, so they appear new and improved.
I've never used them, but I hear a common complaint about them being more difficult to put on a jig head. No doubt shimano already have a new jighead in the pipeline, specifically for this type of plastic.