Color dyes scatter less light. Black and white prints exhibit peak graininess at about .65 density, and color prints at about .93 density. These issues can be factored in when shooting and printing. There are density points that increase or decrease the perception of grain. Steer clear of these points in the final print if you want the perception of less grain or maximize them by giving them the density of maximum graininess.
Granularity is the king of objective grain measurements.
Unfortunately some manufacturers do not supply this information for competitive reasons. This measurement can give you a general basis for comparing grain in films. A microdensitometer is used to measure density. Kodak first exposes the film to a density of 1.0 uniformly and then reads it with a microdensitometer that has a circular aperture of 0.048mm. Remember that the density of the grains is what determines the grain size.