I'm not sure specifically without more context. But often in such a story, there could be a hero or heroine who is facing a difficult situation and trying to survive.
Maybe it's an individual who has made some mistakes in the past and now is in a 'life on the line' situation as a consequence. This person would be the main character as the story would revolve around his or her journey to either redeem themselves or face the ultimate consequence. For example, in a story about a climber who ignored safety warnings and now is stuck on a mountain, he is the main character as the story follows his struggle to survive.
Since I haven't read the story, I can't say for sure who the main characters are.
The main characters could be those who are directly involved in the situation where their lives are on the line. For instance, if it's a story about a sinking ship, the captain, the crew members, and the passengers could be the main characters. They each play a role in the struggle for survival, with different levels of knowledge, skills, and courage that contribute to the overall story.
I don't have enough information to know who the main characters are. It could be ordinary people who find themselves in extraordinary and life - threatening situations, like a hiker lost in the mountains and having to survive against all odds.
The main characters in the 'life line short story' might be people who are facing some sort of crisis. It could be a doctor and a patient if the story is about a medical emergency where the doctor's actions are the patient's 'life line'. Or it could be a teacher and a student if the story is about how the teacher's guidance is the student's 'life line' in academic or personal growth.
Since I don't know the exact 'life in the line true story', it's difficult to say who the main characters are. It could be the workers themselves if it's a story about a high - risk job like working on power lines. They would be the ones facing the challenges and making the story interesting.
Since it's a true story, the main characters are likely to be real people. They could be ordinary individuals who find themselves in extraordinary circumstances. Maybe it's a worker in a high - risk profession, and his coworkers and supervisors are also important characters as they are all part of the environment where the 'life on the line' situation occurs. It could also include people who are helping or hindering the main character's journey, such as medical professionals if the story involves a health crisis, or community leaders if it's a story about a community - wide problem.
I'm not sure as the title doesn't give that away. It could be ordinary people who find themselves in extraordinary circumstances.
Since I don't know the specific story, it could be the person whose life is at risk. Maybe it's a single individual like a fisherman lost at sea trying to survive.
Without knowing the particular 'end of the line story', it's difficult to name the main characters. But if it's a story about the end of a war, the main characters could be the soldiers on both sides. There might be a heroic soldier who has survived until the end of the war and is now facing the aftermath. There could also be the generals who are responsible for making the final decisions that led to the end of the conflict, and the civilians who are also affected by the end of the war in various ways.
I'm not entirely sure without reading the story specifically, but there could be a protagonist who is directly affected by being on the colour line. There might also be family members like a mother or father who play important roles in how the main character copes with their situation.