Dinosaurs were not wiped out at the end of the Cretaceous era when some asteroid or comet hit the Earth and the result send most species into extinction. The reason why it used to be said that dinosaurs disappeared was because the relationship between dinosaurs and their descendants today was not well understood. That changed years ago when it was discovered that a considerable number of dinosaur species that were though to look much like reptiles were, in fact, covered in feathers. It's now thought that the majority of certain groups of dinosaurs were either feathered all over or were born feathered and lost that covering later in life.
The existence of very well-preserved fossilised feathers can allow us to do something that was thought to be forever impossible - to find out the likely colours of some dinosaurs. This can be done because the colours of feathers can be due to their very fine structure. As a result we can know that some early gliding dinosaurs (such as Microrapter) were a combination of yellows and browns.
More detailed analysis of fossils is showing us more about how the species we call 'birds' arose from, and although it's not sorted out fully, there is little doubt that birds are members of a group of dinosaurs called Maniraptora, which includes the fearsome Velociraptors.
The so-called 'dinosaur killer' collision did no such thing. The celestial impact had a dramatic effect on life because what it killed across the world was animals above a certain size. Large land animals could not hide from the fires and impact heat that spread across the world, and in the aftermath large animals could not survive on the limited food that would have been left. What survived were small-bodied species - small reptiles, small mammals, and small dinosaurs, and the dinosaurs that happened to survive were a one group that we now call birds.