There are plenty of note writing applications already available for Linux, if you used to use Windows sticky notes and looking for alternative in Linux then Indicator-StickyNotes can help you with this situation. Indicator-StickyNotes is much better than Windows version and customizable. It allows you to create categories and customize each category as you want like set custom font, font size, text and note color, shadow. Even you can set to default your own created category.
Indicator Stickynotes helps you jot down thoughts, write lists, and make reminders quickly. It is a simple app written in Python3 and GTK3 under GNU GPL-v3 license, some parts of this program has different license (BSD license and GPL-v2). It can work in most of the Linux desktops such as Unity, Xfce, Gnome, Gnome Shell, KDE, Mate, Cinnamon, and so on. You can also contribute to this project in different ways like Translate it to your language; report bugs; feature request; and write code.
Tested on Debian 7, It can work in Debian 8 and related Debian 7/8 derivatives
To install Indicator StickyNotes in Debian open terminal and copy the following commands in the Terminal: