What is the origin of wearing black to funerals?
It is said to have originated from a time when people believed that when a loved one passed away, that the souls of the dead would leave that body any enter the body of a mourning loved one. So people started wearing black robes to hide their faces so that the lost soul would not find them and continue on to the after life. As years went by it transformed into a showing of respect for the dead.
No, men wearing black to a wedding is not an omen. In Western countries black has been the traditional attire for men throughout the centuries, but in these modern times men can wear almost any color and eliminate wearing black. Black use to also be considered a color to wear to funerals, but now most people will wear subdued colors and not necessarily black.
Black is generally considered more for funerals than for a joyous occasion such as a wedding. However, modern times dictate fashion so if a bride wants to wear a nice satin strapless dress and pump it up with a colorful bouquet then it is up to her as to what makes her happy. There is no sinister reason for wearing a black wedding dress.