Neutrals come in all shades - light, medium and dark. Could it be when they say "neutral", they mean not too bold or not too bright? Are they asking for a single color tone-on-tone type of quilt? or do they want some color in it, just not an "in-your-face" color? You could do several different shades of beige, from nearly white to nearly brown, and it would look amazing. As long as you have a good selection of light-medium-dark. A problem quilters often have (including me!)is picking one shade of a color, and one shade = boring quilt!