RGB Digital displays found in most PCs and tablets like the iPad are capable of producing colors outside the Pantone and even CMYK gamuts. This has to do with the fact that displays emit light. The color chart above illustrates this. A display calibrated for print will appear dimmer but closer to what you would expect to see from printed material. Without proper calibration, color will often be off when it comes time to print.
Digital paintings done on the iPad with ArtStudio.
Digital clouds from balcony in ArtStudio on iPad 2
Color Sketch in ArtStudio on iPad 2.