An open source initiative, Tango desktop project is all about creation of a set of design-related guidelines and delivery of consistent optimum user experience for the applications running in different desktop environments. The reason why Tango desktop project is around is for assisting the creation of consistent graphical user interface (GUI) experience for all open source and free software out there.
We all know that the exact feel and look of every application is determined by its several individual components. Nevertheless, it is important to have a certain degree of organization for unifying the structure and appearance of all icon sets that are utilized inside those components.
What Tango desktop project does is that it provides comprehensive icon style guidelines that all designers and artists can adhere to. The sample of every possible style that can be implemented is made available in the form of an icon theme, created around a standard icon naming specification. Furthermore, this project makes available transitional utilities for helping in creation of icon themes for different desktop environments like KDE, GNOME and more.
The project has resulted in creation of a set of icons referred to as the Tango icon library which is also a valid proof of its concept. The project is one of the Freedesktop projects and has close links with various Freedesktop guidelines like the standard icon theming specification.

Objectives of the Tango desktop project
The main objective of this project is to allow for easy integration of software (when it comes to its appearance) by the software developers, with the different desktop computing environments. We all know that there are several visual inconsistencies that arise because of differences between the different desktop environments like Xfce, GNOME, KDE etc. Furthermore, targeting Linux becomes a pretty difficult affair for the third parties, owing to the custom distributions.
What happens in case of Tango is that any desktop project that diligently abides by the Tango guidelines has a feel and appearance matching very well with the other applications and icons that also follow the same guidelines.
The style itself doesn’t aim to achieve visual uniqueness, so as to distinguish itself. Rather, it is the secondary aim of the Tango project to develop a standard style which makes applications appear alright when they are running on common operating systems at that particular time, in a manner that independent software vendors don’t find their applications to be out of place when they are running on different environments like Xfce, GNOME, Mac OS X, Windows XP or KDE.
It’s not just about the visual guidelines, the Tango project also aims at providing common metaphors for all the icons. As also mentioned earlier, at its core, Tango abides by the standard icon theming specification (of Freedesktop). It is engaged in active development of Freedesktop’s standard icon naming specifications too (involves naming of the most commonly used metaphors and icons).

All in all, the Tango desktop project delivers the following:
- A subsystem that helps in standardization of toolkits upon a common icon naming structure.
- A cross-desktop and generic human interface guidelines.
- A comprehensive set of stock icons, mime type and application designed with the help of a well-defined style-guide.
- A recommended default native appearance.

A large number of free software projects like GNOME, Scribus and GIMP have started following the guidelines laid out by the Tango desktop project for their own icons. In addition, Mozilla Firefox 3 and ReactOS also make use of Tango icons when they are unsuccessful at finding the installed icon set at the user’s end, and also in case when the icons are not covered by the concerned icon set. Even proprietary closed source applications like Medsphere OpenVista CIS and VMware Workstation 6 can make use of Tango desktop project icons.
People who are involved in the Tango desktop project are user interface designers, artists, engineers and volunteers who are all involved in it for the love of it! Their team also welcomes experts from all backgrounds to assist in production of a native, open structure and appearance by asking them to contribute to the various guidelines, artwork and help in improving the applications by spreading the word.

A bit about its history
The Tango desktop project icons were released originally under the license of ‘Copyleft Creative Commons,’ however were later released in the public domain in the year 2009 so as to allow for their easier reutilization.

Something about its theme guidelines
Tango desktop project has a common color palette as it is necessary for it to have a consistent appearance across all the icons. The visual side of these icons is heavily determined by the usage of these colors. Its color palette comprises of 27 RGB colors. Please keep in mind that majority of desktops allow 24 bit RGB icons.
An icon has several unique attributes which defines it as a part of the Tango desktop project, including aspects like lighting and perspective. Let’s go over some of the key visual aspects which define these icons’ styles:
Object outline – All icons belonging to the Tango desktop project feature a thin outline in order to improve the contrast factor. In case of low resolutions, that stroke size is of 1 px. It remains fixed at 1 px and doesn’t scale along with the icons. The outline’s color is a slightly darker version of the icon’s key color. It is achieved by retaining the saturation and hue of the primary fill color and reducing its value to around 20% of the original.
Glossy reflection – These icons make use of glossy reflection only in case of objects that have reflective surface in the real world, for instance metal, glass, plastic etc. Hence, a piece of paper wouldn’t have any glossy reflection.
Highlights – The objects’ edges reflect light a little more owing to the fact that the observer’s position in relation to the light source is mostly ideal for reflection. When it comes to the highlights, the theme makes use of the Winstripe / Thunderbird Pinstripe / Firefox style designed by Stephen Horlander and Kevin Gerich. These styles move away from the reality by creation of second inner outlines of the objects. Such stroke is quite subtle and may not be sufficiently visible on certain matte objects.