Earlier quoted context omitted.
Beware the effects of incident lighting on colour perception. As a human, you do a lot of processing you're not even aware of to normalise the colours you perceive. Cameras cannot do this (without calibration), so if the incandescent/flourescent/daylight/sunlight mix and intensity is different in the store to your house, you could end up with a very different shade.
Matching the appearance of existing paint / colored surfaces is difficult. You need data on the variation of colour, intensity and reflectance as a function of viewing and illumination angles. Not something a mobile device can do. The device described in this paper can: (note: I am not affiliated; just out of interest) http://www.pro-lite.co.uk/File/RAD%20Imaging%20Sphere%20Pape... [Edit: spelling]
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