That argument usually only comes up for war-oriented games, or games that have a more bleak atmosphere/ setting. Killzone 2 was a perfect example. The color pallet seemed so limited because the planet Helghan was just such a dreary, dark, and polluted place that a grey/ black color scheme only made sense. Same applies to Gears 3 with it's mostly brown color scheme. Honestly I think people who care about color schemes are stupid. Jut play the damn game. If you want vivid color, go outside.