Depending on the formality of the wedding and any personal issues with mobility, the grandmother of the bride may choose to wear a long dress, a shorter dress or a pantsuit to her granddaughter's wedding. Color is optional, with only a few restrictions.
If the mother of the bride is wearing a long dress, it is acceptable for the grandmother of the bride to follow suit. If, however, the grandmother is afraid of tripping, she may opt for a tea-length or knee-length dress or a dressy pantsuit. If the mother is wearing a short dress, the grandmother should wear a shorter dress or pantsuit. She does not need to go dressier than the mother.
The grandmother may wear any color she feels is flattering to her; however, she should not wear a shade that too closely matches that of the bride or bridesmaids.