In traditional wedding etiquette, the choice of dress for the groom's mother is subtly driven by the mother of the bride. Though modern etiquette is more flexible and acknowledges that the groom's mother must also feel and look good, the central courtesy still remains the same: the groom's mother waits for the bride's mother to choose a dress first and initiate communication. In the end, following dress etiquette helps pave the way for good future of communication between the bride's mother and the groom's mother.
Traditionally, the mother of the bride purchases a dress first. She then notifies the groom's mother of her dress choice, including details such as the style and shade, so that the mother of the groom can purchase a dress that complements, but does not exactly match, the mother of the bride and the attendants.
Today, the mother of the groom has more freedom to pick an outfit that she feels great in and is appropriate for the season, time of day, and formality of the wedding. Still, she should remain sensitive to the mother of the bride's dress choice and wait to hear from the bride's mother before selecting a dress. This courtesy also prevents clashing, overdressing and other fashion faux pas and is viewed as a friendly gesture between future family members.
If the bride's mom has not contacted the groom's mother in a timely fashion, it is acceptable for the groom's mother to initiate communication and discuss details pertaining to the dress. It's also acceptable to contact the bride if the groom's mother has still not heard from the bride's mother about 4 months before the big day. When choosing colours, traditional etiquette suggests avoiding dresses that can rival the bride, such as white, champagne and ivory. Also, black gowns traditionally suggest mourning and red gowns or other flashy colours are inappropriate. However, today some of these colours can be worn in good taste, so consult in the bride before you do your shopping.