I ordered two halves of a gear for a project I was working on. The two halves were printed out of SLS nylon and one half was dyed black whereas the other was kept natural.

I left them bolted together for a bit over a year and this happened! Some of the dye from the black half leeched into the white half, permanently staining it.
For some context, SLS nylon can only be printed in white and the the only way to make it take on other colors is to boil it in Rit dye.

It's interesting to me that this can happen at all. Just thought I'd share.