On this post I will show you how to install Telegram-cli using a Raspberry Pi 2 model B running Archlinux as well as how to trigger events as turning on an LED, receiving temperature information and taking and receiving a picture using Picamera.
Most electronic applications require light indication of some sort not to mention the trivial power ON lamp. As single color lamp can bear two states of information. Several small embedded applications, apart from the ON/OFF states used to produce different blinking patterns in order to convey more information to the user. The RGB LEDs are multiplying the information that a single source of light can produce (which can also be increased using blinking patterns).