I purchased the app specifically so I could find the closest match to an RGB value. Though the description says it will do this, it would only take CMYK as input. (Update: based on screenshots it appears there is a selection for RGB at the bottom of the screen, but on my iPhone 5 I am unable to see those buttons, which means I am stuck with the default CMYK sliders) User interface is difficult. On the flip side, if you have a Pantone number it will give you an RGB value. That is useful too, unfortunately not what I needed when I bought it.