According to the Hertzsprung-Russell Diagram, Mystery Star would be a Blue Giant because it is located in the upper left region of the diagram, indicating that it has a high temperature and a significant luminosity.
I know this because Blue Giants are characterized by their high temperatures (typically over 10,000 Kelvin) and their large sizes compared to other types of stars. If the mystery star exhibits both high temperatures and luminosity, along with a brighter appearance in the night sky, these are strong indicators of it being a Blue Giant. Additionally, if the star is relatively young, this also supports it being a Blue Giant, as they have shorter lifespans compared to other stars like Red Giants or Main Sequence Stars.