I wanted to ask opinions. My future MIL decided to get a mostly plain black dress with some silver sparkle on top (just the chest area, the rest is plain black). My ceremony is in spring and the ceremony starts in the afternoon and the reception is in the evening. It is formal. However, my colors are purple and white. My first reaction was that she did it b/c she is in "mourning" and moms of brides and grooms don't typically wear black. Am I overreacting? Is it acceptable in this situation?