Is it permissible for Muslims to help their colleagues travel to Western countries for study and work, given concerns that some of them may fall into sins there, or does averting harm necessitate closing this door?

If the person who is to be assisted in traveling to the lands of the disbelievers meets the conditions outlined in the fatwas — even if based on an educated guess — then assisting him in travel is permissible. Otherwise, it is not permissible.