What looks good on a sample paint chip at the paint store might look completely different from what you remember after painting with it, so it's good to have as accurate a resource before applying any new colours. The Color-Helper is an electronic device much like those used by graphic designers for colour matching with six features to help your interior colour-coordinating plans...
The Color-Helper is a colour matching scanner. You can use it on any surface, including walls, objects, colours from printed sources...even your pet if you can get them to stay still long enough. The unit contains 13,000 colors from all of the leading paint manufacturer and allows you to store and compare using an internal comparison feature (you can store up to 9 colours). The unit can also recommend whether colours are harmonious, using a system that is "based on decades spent studying how color affects mood and behavior the Ultracolor harmony system can predict the reaction most people will have to a color scheme." You get a thumbs icon when you've matched the right colours; how affirming.
And if you're poor at matching colours with one another, the Color-Helper has a suggestion feature, offering up to 27 colours to match your initial choice. Finally, the small handheld unit can get you started with programmed colour schemes, including monochromatic, complementary and adjacent colour schemes for your painting projects.
The little unit isn't cheap....$229. But the manufacturer is offering a $40 discount by just filling an online survey of four questions.