I know it's a list of desktop apps, but I just recently launched a quick reference (iPhone) app for iOS devs: http://www.idev101.com/app/
The color picker is my personal favorite. It'll convert between hex colors, RGB and HSB. Plus it shows the UIColor code for whatever color you're previewing.
The color picker is my personal favorite. It'll convert between hex colors, RGB and HSB. Plus it shows the UIColor code for whatever color you're previewing.