PurpleRestore is a tool made by Apple and is used for flashing iDevices. It provides far more customization than iTunes, and it is usually used to flash internal firmware to prototypes.
This tool can (and is meant to) handle multiple restores. When performing restores PurpleRestore color coordinates the device in the table and when the device is about to receive the AppleLogo it will turn the background color of the screen to the color assigned to the device. Like iTunes, PurpleRestore communicates with iDevices using a usbmux connection.
"PurpleFAT" is an Apple Factory Activation tool, assumed to be used in factories for UUT's (units under test). If the unactivated device is plugged into a computer and the software is run, it searches for the device and would activate it (Seems not to work and just plays a sound saying "Oh nooh!") PurpleFAT needs an activation sever. https://albert.apple.com/WebObjects/ALUnbrick.woa/wa/deviceActivation does not work.
Application can be locked for some security reasons, and requires a passcode when unlocking the interface (This passcode is stored in a string, when dissasembled can be found at __text:00003089).
PurpleSNIFF is a tool made by Apple to read identification and diagnostic information from the device. The tool is used by Apple engineers as well as factory workers at Foxconn/Pegatron. It's included in the RestoreTools package.
Like iTunes, PurpleSNIFF communicates with iDevices using a usbmux connection.
PurpleBuildSanitizer is an Apple internal Mac application for stripping internal builds for internal use. When creating a stripped bundle, it names the folder like so, N92-INTERNAL-INSTALL-iPhone3,3_4.2.6_8E200_Restore.