What method yields best result for washing breads? I've seen many bread recipes and they used different combination as egg-wash. Egg white plus water, egg yolk plus milk, beaten egg plus milk or water, and I myself sometimes give it a sprinkle of saffron ti get a goldener final result. Is it better to use egg white or egg yolk? Milk or water? Do they make any big difference or they are all the same?

The egg-wash I used for these croissants was a beaten egg plus a few drops of milk and a pinch of saffron. But sadly they are not as golden as expected even though I turned on the heat coming from up for a few minutes (oven's temperature: 450F):
I have always used egg and milk. Two thirds egg to one third milk. Use a spray bottle to ensure that you get a nice, even coverage.

Also make sure that you have a full proof on your goods, because (obviously) anything that gets exposed to the heat due to oven spring will not have color.

Just the way I have always done things (and I used to work in some pretty nice pastry shops back in the day).

EDIT:

Just noticed the comment from sour d'oh... Should've mentiontioned that stuff myself... Very important. The higher the fat of the dairy, the better the color (use a high fat cream instead of milk).