Bolians distinguished themselves by their light blue skin with a vertical cartilaginous ridge bifurcating their heads and running down to the middle of their chest. (VOY episode: "Someone to Watch Over Me") Their pulse could be detected by feeling along their ridge. (DS9 novel: Avatar, Book One) Their cobalt-based blood chemistry is compatible with Andorians, but toxic to Vulcans.
Bolian mythology paints a rich and harsh beginning for their people. It is believed that it was due to the harsh weather conditions that three brothers set out to sea in hopes of finding a better land to settle. Sailing each in their own directions, they discovered the three continents that make up the surface of Bolarus IX, thus the first tribes were established. Though there were territorial wars as the Great Migration continued and tribes met one another, eventually the cooperative nature of the inhabitants lead them to work in unity.
These loose alliances would eventually grow to form three nation states, these states grew quickly, although they worked together they would usually view themselves as superior to the other states. Even if this period of history is viewed as turbulent, it also lead to some meaningful technological and cultural breakthroughs.
During the subsequent era of peace that lasted 400 years, they achieved spaceflight and explored their solar system. They had established research colonies on two planets and were working on warp technology when the Iren and Uzor, warring species of a neighboring system, entered the Bolarus system. Two of the main nation states made contact with the species and would choose a different side. This lead to turmoil among the Bolians. The third nation state isolated itself as they feared the chaos brought to the planet. (Decipher RPG module: Starfleet Operations Manual, Last Unicorn module: Planets of the UFP)
The presence of the Federation brought the nation states back to the negotiation table and pushed the warring species away from the Bolarus system. After some time the Bolians were made a special offer, if they could create a single government entity they would be taken into the Federation.
Since joining the Federation they have contributed a great deal including development of advanced antigravity technology and a new dilithium crystallization process. (Decipher RPG module: Starfleet Operations Manual, Last Unicorn module: Planets of the UFP)
In the Kelvin timeline, Bolians were among the many species visiting, and living on, Earth. In 2255, the bartender of the Warp Core establishment on Starfleet Academy grounds was a Bolian man named Bom.
The planet Myrmidon is considered to be the Bolian spiritual home, due to the Bolastre Crown of the First Mother resembling Bolian royal jewelry in the Orezes Codices sacred text. Archaeological research indicated that the Bolians and the Bolastre had a common ancestor. Nearly fifty million Bolians lived on Myrmidon. (TNG novel: The Genesis Wave, Book 1)
Typically Bolians were gregarious, hardworking, and meticulous. They enjoyed cooperation and work group dynamics. However, you can always count on a Bolian—their selflessness is legendary. (Decipher RPG module: Starfleet Operations Manual)
Bolians work well in professions that privilege group cooperation and group effort; every branch of starship service suits their desire for teamwork and structure. Bolians also make good merchants, scientists, and soldiers. Bolians enjoy diplomacy and some of them are quite good at it. Bolian nationalists have occasionally joined criminal gangs such as the Orion Syndicate—they make good rogues in those cases. (Decipher RPG module: Starfleet Operations Manual)
Starfleet Academy was accepting Bolian cadets as early as the 2270s. (TOS novel: In the Name of Honor) A Bolian competed in the 2376 Academy Marathon on Danula II. (New Worlds, New Civilizations short story: "The Footfalls of Tradition")