Tell them that you feel it is a universal sign of professionalism when it comes to appearance and that you wear it because professionalism is important in the workplace.
bow tie for really fancy, tie for relatively relaxed
depends on the shirt and tie. but make it a thin tie!
Gray.
suit with a green tie
Probably any tie but it depends on where you are going like if it is fancy place or not
When they wear out.
Yes it is very attractive!
A normal tuxedo with a black tie or bow tie. You could go for matching outfits or a complete contrast. E.g - Black shirt with a white tie
If you are not in the wedding party and there is nothing mentioned about 'white ties' then no, you should not wear a white tie.
In some countries, you should. In Sweden, the closest relatives to the deceased traditionally wear a white tie. That is, children, parents, husband, wife or siblings. Others traditionally wear black tie.
A tie should be worn to graduation only if it's a formal affair. These days it's mostly a "wear what you want" setting.
Proffesional, suit and tie