Last weekend while visiting Legoland Germany, we found the following pieces in the discount crates:
They are white 1x1 bricks, with the top part (and stud) in light bluish gray.
What would be the origin of these pieces? How are they produced?
Please excuse my answer, because it is pure speculation.
Unfortunately, I don't know anyone that works for LEGO Germany, but Plastic Toy Industry-wise, I have a few friends that work at Hasbro headquarters in Rhode Island, USA, where their casting department spits out many prototypes of toys in the oddest of colors, where the reasoning behind doing so could be varied.
They may need to:
Somewhere in my basement I have two Transformers entirely purple given to me by my friends at Hasbro.
So, in review, it might be rare for us outsiders to come across these items, but I don't think this is an odd thing for a company in the Plastic Toy industry to do when bringing an idea to market, thus ending my speculation on why these pieces have different colors.
Looks like they may be spray-painted? Perhaps for a store display or mosaic? – TheBrickBlogger Jul 14 at 0:40
I agree with this hypothesis. In particular, the pieces would have been assembled and then spray painted. This accounts for the faint tinge of gray on the top edge of the sides of the pieces (paint in the gap between adjacent bricks), and why some of the pieces (right side of the photo) have gray sides.
The tops of the studs look slightly less sharp than LEGO plastic molding usually is, which would be due to the paint slightly rounding everything over.
It is also unlikely that this effect would have been produced by regular injection molding, because the plastic does not enter the mold in neat flat layers so you can't do this by just putting two different colors in. "Overmolding" can create an object with two plastics stuck together, but they would have a crisp edge usually with a detectable seam, not the faintly fuzzy one here. In any case, some very unusual process would have been used, and I doubt that TLG would have gone to the trouble.