* Stars that *appear* blue: In this case, the closest blue star would likely be Sirius, the brightest star in the night sky. Though it appears blue, Sirius is actually a white star, but its intense brightness makes it appear bluish.
* Stars that are *actually* blue: This gets a bit more complex. While Sirius is white, there are actually many blue stars closer to us than Sirius, they're just much fainter and harder to see with the naked eye.
To give you a more precise answer, we'd need to define what we mean by "blue" in terms of a star's spectral classification.
For example:
* B-type stars are generally considered blue and are quite hot. However, there are no known B-type stars within a few light years of Earth.
* O-type stars are even hotter and bluer than B-type stars, but they are extremely rare and far away.
Therefore, without a specific definition of "blue", it's difficult to say definitively which blue star is closest to Earth.
