I mean I'd just be happy with natural tones of brick, stone, masonry etc; not necessarily unnaturally bright tones. Those are pretty timeless finishes that add colour and texture. In addition to resale beliefs, I have to wonder if grey finishes are just cheaper to produce due to fewer pigments needed, or something along those lines. Entirely speculation, but I would certainly believe that to be a factor.
edit. I should add, I'm not wholly against monochromatic buildings. Quite the contrary, I love the pop of bright white buildings or jet black. It's the endless shades of grey that are dreary and depressing.