I am always hitting the Safari icon when I mean to open Mail, and vice versa; I blame the icons' similar blue hue. I set out to change one of these icons, but without the effort required to jailbreak my iPhone. What I found was a free PC/Mac app called iPhone Explorer and the realization that I would have to live with the blue Safari and Mail icons.
Using iPhone Explorer, you can swap in new icons for your iPhone, iPad, or iPod Touch apps, but only for third-party apps. Native apps like Safari and Mail can't be accessed with iPhone Explorer. Should you want to change the look of any of your third-party iOS app icons, however, here's how: