Do the inside of the pipes have a different color than the outside? If so, they are probably discolored.
I could not look inside the pipes before because the pipes shown in first photo of this thread were not mine. I only had the lighter gray ones but I got the other two variants recently. Now, with the evidence I can confirm that
there were three colors of pipes in set 4105: brown, lighter gray and gray.No yellowed, no discoloration. They are just two different tones of gray.
![](http://i1164.photobucket.com/albums/q564/BiktopP/4105/DSC04372_zpssyudih0x.jpg)
In real life the difference is quite obvious. It is like make a comparison of some Playmo dolphins or sharks that do have variants in gray.
Actually, there are three box versions in Playmobil Collector's Guide 1974-2009 , 3rd edition. I wanted to make a correlation between the boxes and the pipe colors but I got a 4th box version not shown in the guide. See below. So, I just can say that
two different tones of gray did exist.
![](http://i1164.photobucket.com/albums/q564/BiktopP/4105/DSC04396_zpsy5ygrzpo.jpg)
![](http://i1164.photobucket.com/albums/q564/BiktopP/4105/DSC04401_zpsdtvtmwdq.jpg)
![](http://i1164.photobucket.com/albums/q564/BiktopP/4105/DSC04381_zpshvvzvsow.jpg)
No set number in box
![](http://i1164.photobucket.com/albums/q564/BiktopP/4105/DSC04385_zpsfqpsbshf.jpg)
I got brown pipes in this box.
Outline number (and the legend "tracks not included" in 6 languages)
![](http://i1164.photobucket.com/albums/q564/BiktopP/4105/DSC04390_zpsvk7arsyd.jpg)
I got light gray pipes
Outline number and no legend. Not shown in Collector's guide
![](http://i1164.photobucket.com/albums/q564/BiktopP/4105/DSC04383_zpsluwt4m9m.jpg)
I got gray pipes
Black number (and the legend "tracks not included" in 6 languages)
I do no not have this box version but it is shown in Collector's guide.