http://www.colorschemer.com/ ( Window)
This is the main window with the Color Wheel tab selected. A color wheel is created starting from your selected base color.
Mix two color to gether, will have from light to dark.
Use the PhotoSchemer tool to build unique color schemes based on any picture, image or photograph .
Just drop an image onto the program and let the PhotoSchemer do the rest!
For your Iphone, I checked on Iphone, it's free on App Store, and really helpful too ! Bravo ^o^!