Allowing a document to be rendered in grayscale would enable visual queries to receive clearer attention. For example, if you have a floor plan and want to higlight free desks, then the desks could render in green and the rest of the diagram in gray(scale). This is possible in Visio currently, but means that every shape needs to carry both its 'normal' RGB and its grayscale equivalent. This is probably better attached at layer level and could then be used in Desktop, Online and PowerBI.