Grave Betrayal vs. Blightsteel Colossus
Consider this portion of the text on Blightsteel Colossus.


  If Blightsteel Colossus would be put into a graveyard from anywhere,
  reveal Blightsteel Colossus and shuffle it into its owner's library
  instead.


This text creates a replacement effect. A replacement effect "watches"
for an event to happen. For example, regeneration is a replacement effect that watches for the creature to be destroyed.

The rules for replacement effects neatly state that the event being replaced never happens. 


  614.6. If an event is replaced, it never happens.


So, when Blightsteel Colossus starts to head for the graveyard, instead, he is revealed and shuffled into his owner's library. The event that got replaced never happens.

To die in Magic has a specific meaning:


  700.4. The term dies means “is put into a graveyard from the battlefield.”


Blightsteel Colossus never went to the graveyard, and so Blightsteel Colossus never died. Therefore, Grave Betrayal never triggers.