If a blue star is supposed to be the hottest, why is the color blue considered to be cold?

Answer 1

Considering a colour to be cool or warm has nothing to do with the temperature of a star.

Starlight is a mix of all colours (from red to indigo) just like our sun's light. Each colour is a range of wavelengths of energy, and we can see them in a spectrum (e.g., with a prism or as a rainbow).
As temperature rises, the amount of energy given off moves up the spectrum from lower energies (longer wavelengths such as red) to higher energies (shorter wavelengths such as blue). When a star is hot enough, there is so much energy in the light that not only does all the light combine to create white light, but there is additional energy in the blue/indigo end of the spectrum that 'colours' the light a little.

Answer 2

Blue is the colour of a clear winter sky or an icy pool. Red is the colour of blazing fire. We have psychological attachments of colour to temperature which runs opposite to the individual photon energy (=frequency) that determines colour.

Also, if you are hot you turn red. If you are very cold you turn blue. This is a blood effect and nothing to do with light energy.

Answer 3

Two entirely different concepts.

Answer 4

Frankly I have worried about that also, and it confuses me.