If a star has a negative $B-V$ value, what does this imply about its color and temperature?

Answer

It is a hot, blue star

A negative color index ($B-V$) results when the blue magnitude ($B$) is smaller (brighter) than the visual magnitude ($V$), which is characteristic of hotter, bluer stars.

If a star has a negative $B-V$ value, what does this imply about its color and temperature?
astronomystarbrightnessScalestellar magnitude