From what I can see; they all seem to be similar but from different oem vendors/brands; the top 4 listed, all say "exact fit". Spec wise; some are 1.2 to 1.6 bar; while one is 0.3 to 0.6 bar. I guess the colors denote the bar ratings; green 0.3 to 0.6 bar; black 1.2 to 1.6.
. Advance Auto Parts: Search Results for oil pressure switch
Here is one listed from a online dealer; the part numbers are listed, I guess if you wanted to make sure to get the correct one... you could check with your local Volkswagen dealer.
Thanks man! They actually had some factory spec ones in stock at my local parts shop. I think it was like 13 bucks. I guess the green ones are for aftermarket ones and black stock. Thanks for the advice.