Westone is a truly amazing company. I asked them about the availability of the new star tips and they offered to send me some samples. I was expecting couple of tips but today I found out that they actually sent me 20 star tips (10 pairs) free of charge. 10 silicones and 10 foams.
New star tips are really good guys! Everybody should get their hands on them.
Until today, I have been using the grey mushroom tips. I tired the new silicon tips with red, blue and non-colored stem. Blue stem is pretty good, opens up the sound, increases the soundstage significantly and adds quite a bit of energy to the highs. However bass response became softer compared to the mushrooms. It may be related to isolation though. I felt like they isolated quite a bit less than the mushrooms. They go deep into my ears and are quite comfortable though.
Red stem tips great. Bass is as strong as the mushrooms if not stronger. Soundstage is again much more spacious and there is again quite a bit of newly discovered energy up in the highs same as the blue stem tips. Isolation is top notch. However I found them a little bit too long for my ears. They really go deep which is not bad considering W4s have short nozzle.
Non-colored stem tip is the absolute bomb! Sound is same as the red stem tips. Punchy bass, amazing soundstage, clarity and quite a bit of energy in the treble region. However these are much shorter than the blue stems yet they isolate more or less the same. They look and sound like upgraded mushroom tips and they are actually more comfortable than mushrooms for me.
There are 2 more silicon tips but didn't bother too try them. One is too large (orange stem) and the other one is too tiny (green).
I haven't tried the new star foam tips yet as well.
Just for clarification because someone else mentioned it a while back, the different star tips are NOT intended to create different sound presentations, etc. Any variation in sound has to do with the fit (or improper fit) of whichever star tip you are using.