Colour for mother of the bride?

I think this obviously depends on the exact shades of red and grey etc that you have your bridal party in, but in terms of colours that would tone in well, I'd go for slightly darker or slightly lighter than the colours you already have.

So, dark burgundy or wine tones, fuchsia, dark pink, silver, pewter, dove grey, mauves, dusty pinks, and that weird taupe-pink-grey colour that doesn't really have a name, haha. I've found some pictures of the colours I'm thinking of (ignore the style of the dresses). Ba

I love how my mom looks in black. With your colors, I would suggest it but not require it.

I'm sure you're not making your mother wear something she doesn't want, and she asked for your opinion. Based on the time of year and your colors, I would go with a gray or black!