Chris Peterson wrote:
The reason why an 18,000 K blackbody is generally considered the most blue (and why most people see it that way) is that this is the temperature where you have the most "blue" (450 nm) energy in comparison with longer visual wavelengths. As you get hotter, the energy across the visual spectrum gets flatter, with relatively more energy at longer wavelengths compared to blue (you always have more in total at the short end, it's just that the distribution gets flatter).
I have to differ. The form of the blackbody function shows that its slope across the visible (or any other range longward of the peak) saturates toward high temperatures, so that arbitrarily hot blackbodies are no redder than cooler ones. This plot uses the standard IDL astro library function
Planck, and compares blackbodies at 10,000, 25,000, 50,000, and 100,000 K. They are normalized to the same observed flux at 10,000 Angstroms = 1 micron to show the optical slopes more clearly. This continues to steepen to shorter wavelengths (become more blue, if I take the shorthand astronomer's parlance and sidestep perceptual nuances), albeit with diminishing returns at high temperatures.