This is a cool idea but I don't think it works quite right, matching RGB color is a perceptual thing, there's no absolute "starbucks green" that you could displ

This is a cool idea but I don't think it works quite right, matching RGB color is a perceptual thing, there's no absolute "starbucks green" that you could display on a monitor. Even a calibrated monitor in controlled lighting conditions is still calibrated to something (like a film stock or a certain printer profile). I think a better way to present this would be to show a photograph which incorporated the logo (e.g. a Coca-Cola billboard in a city on a sunny day) with the grey logo, and then have the user color-correct the logo until it matched the perceptual reference of the context that it was in. The "coca cola red" in RGB values would not be pure red but I think the user would probably have a better chance of making it "look correct" in the photo (thus matching the color values in the original photograph) than trying to match it without any context. Would make a neat experiment, too.