As it is a quilt which will bring back special memories of your mum when you look at it...why not try and sash it with a colour that you associate with her...what was her favourite colour or did she have a dress or coat she loved.
My mum adored green, all shades and had a red coat that I loved her in.....see where I'm going...wishes you much love with it...whatever you choose it will always be special.