By the order of the classic rainbow - first com the Ara. Heirs of Khas, dark-grey striped guys dressed in bright red clothes. In my headcanon these guys chose the hottest equatorial regions of Aiur as their territory and lived there for millenia. Their scales colour is great disguise when it comes to hunt in dark shades of jungle. During aeon strife they were desperately fighting with many neighbours, longing to occupy this equatorial grounds, but despite Ara had never been martial, they were genius strategists and diplomats as well, so they established a powerful alliance with the Velari tribe against the other tribes, and after the Khala came around they were chosen as Judicator tribe, from which came many war counselors (including the only ingame Judicator Aldaris), prosecutors, inquisitors, etc. Next ones - I really like how these came out - the Auriga with sand-like skin and bright eyes. This martial tribe occupied wide territories of deserted regions, full of sun and sand, and stood in a permanent conflict with Akilae and Velari, also longing to take their place under neverending sunlight. Aeon strife forged Auriga as mighty warriors and creators of best armors and weapons. At the end of this destructive conflict they became allied with Ara and Velari and the other martial tribes were outnumbered. When Khala unified everyone, the Auriga turned into best soldiers and at the same time best armor engineers, so Khas divided the Auriga in two castes - Templar for the ones with high martial potential, Khalai for the ones physically weaker. This tribe produced not only one of the most loyal warriors of the Conclave, but also the best phase-smiths that eagerly improved protoss weaponry through millenia. I personally refer ingame Karax to be one of them, because I totally can’t see him as a Furinax. Yellow is for Velari. Beautiful sand-people with bright khaydarin-colour eyes and light scales, variating from shades of yellow to almost grey, sometimes covered with stripes, inherited from genetic contacts with other tribes. During the aeon strife they occupied wide territory, neighboring and being in permanent conflict with Akilae, Auriga and Ara. Through these days they did not give themselves into sciences, but practiced multiple combat styles and psi  manipulations, that made them most deadly, when battles on ground occured. By the end of aeon strife Ara forged an alliance with them and started the triumphal move through the deserts that were well known home for all the Velari. Surrender of other tribes was only a question of time. When protoss unified, Velari became proud part of their military forces, and their combat styles became part of all Templar spirits. When protoss developed space travelling, many Velari were eager to be with first explorers, and later they became best pilots among children of Aiur. If I remember things right - the Great Executor Tassadar origins from this tribe (and in SCI we usually play as Velari protoss in campaign), as well as that odd lady Rohana. Green is for Akilae. Inhabitants of subtropical zones, hiding in shadows among the rocks. Almost like Ara, they've adapted to shady yellowish green surrounding of rocks and grass, so colours of their scales variate from light brown to shades of green. Being in the heart of all major conflicts of aeon strife they still had time to develop sciences and philosophy, which was quite inspiring on the battlefields. Being the tribe of mighty warriors, they were also tribe of mathematical genies. When Khala came around, Akilae were determined as Templar tribe, but it occured quite often that their children became great thinkers and were accepted as Judicators. But many of them felt uncomfortable in the great unity, so a lot of Akilae in fact became Dark Templar afterwhile. It seems that in SCII most protoss in our possession belong to this tribe, along with Artanis and Selendis themselves, and I personally refer praetor Fenix to them also. Teal is for Sheddar (what? who? ah, its a tribe from fanon expansion set, if someone recalls). These are peaceful inhabitants of cold swampy misty lands with blue eyes and blue skin. As well as the Venatir they tried to stay away from the others during the aeon strife and took their time to explore properties of plants around them. They succeeded in finding many medicines and creating clothes to protect themselves from surrounding nature. And also - they succeeded in hiding among it. Other tribes just never knew that they were around when they tried to explore their territories. When protoss society became unified with Khala, Sheddar never tried to get any power, prefferring to proceed their peaceful existance and ready to share their practical abilities with the others, so their tribe found itself in the Khalai caste and served mostly as healers, tailors and entertainers. I personally refer poor Lasarra to this tribe - as long as she was able to survive among others on cold planet Kaldir, it seems logical. And here go the blue guys - Sargas, willing inhabitants of the coldest grounds of Aiur. During the aeon strife they were quite far from the main conflict and successfully defended themselves inside their fortifications. They evolved to be strong and brutal like true Spartans, unaccepting weakness among them. Eventually they were neighbours of seemingly fragile, but wise Venatir and, while Venatir did not demonstrate any aggression, offered them protection. That was not a military, but a cultural and practical union, where they shared methods of survival in rigid surroundings. They developed shielding technics and were the first ones to create and use pylons as powerful energy sources, able either to keep them warm, or to charge weapons. When Khala came around, a lot of Sargas reacted very negative and, while Venatir were the main inspirers, they were the main force of those, who opposed the unity, offered by Khas. Almost half of tribe left Aiur at the day of first Dark Templar exile. But those, who stayed, became the most loyal and fierce warriors of Aiur that quickly removed the heretic claim from their tribe.  Violet Furinax, inhabitants of middle continental zones - not too hot, not too warm, but still enough motivating to construct not only defensive walls, but houses with possibility to regulate the conditions depending on period of the year cycle. Their scales variate from shades of grey to lavender violet. Adapting the volatile conditions, Furinax succeeded in creating technologies of matter transformations that then resulted in first materialization matrix and teleports. Khala gave them place among others as the most devoted members of Khalai caste. Many Furinax served among all others as architects, chemists, and then centuries after - warp rifts and space gears specialists. It is ironic there is no brown colour in the rainbow but. Here come the Venatir, gloomy secretive light-brown guys from the north. They were the least successful in tribal wars, so they had to move away from the lands warm and full of light to the cold and gloomy lands with polar nights and northern lights, where noone would follow them. Their scales colour recieved a shade of brown, but is mostly light - like a naked tree. Difficulties of life forced them to develop the technologies faster, so the Venatir became experts in manipulating with energies of khaydarine crystals. Also they've discovered the possibility of unifying their minds in Khala-like web even before Khas made his discovery, that made them the best among all protoss at hiding their thoughts. Their powerful minds conquered them the deserved place among other Judicators. Eventually, that made many of them to become the main ideologists of the Rash Nidal - the first path of darkness, that denied power of Conclave, and when the first dark templar were exiled, a lot of Venatir were among them, so the reputation of the tribe was worse then ever. But still, Venatir became best experts on psi-energy manipulations, mind-melding and astrometric sciences. The colour pattern is never full without black and white. And white is for Shelak. Keepers of the knowledge, meditative highlanders and philosophers. Their scales' colours variate from silvery grey to off-white, sometimes with pale stripes, perfect to hide in rocky grounds. During the aeon strife they used to be the main pretendants to shift Ara from warm and shady jungle, but never succeeded, so they had to stay among the rocks, that surrounded the humid valleys. While not being strong and numerous enough to stand real conflicts, they concentrated in keeping and learning the knowledge of the Xel'Naga and later of all the other tribe, so when the Firstborn were unified with Khala, these Judicator tribe gave way to many historians, librarians and great thinkers. Khas himself, although originated from Ara, spend much time among them, and their high rank in Protoss society was his gratitude. And the last one, black is for Kanimai (what again? yes, again a tribe from expansion set) - tribe, that is actually a mix of Protoss of different tribes, that tried to overcome the major conflict and create a new peaceful unity in the middle of aeon strife. They had to leave the territories of conflicts and move to cold misty mountains on far south, where they had to learn a lot about properties of minerals and surrounding liquids that were not always harmless. Their appearance is variative, cause inside their newly created society occured intensive cultural and genetic mixture. When Khala came around, they were accepted as they were and castes of their children were determined individually, but mostly they were Templar or Khalai. Despite such controversial history, Kanimai proceeded as separate tribe with its specific features. Among them were many of the first explorers and colonists, resources developers and nexus operators.