Figure: Spectra of three black bodies with different temperatures

The graph above shows intensity vs. wavelength for blackbody sources at 12000 K, 6000 K, and 3000 K. The area under each curve indicates the total flux - the amount of energy emitted per square meter. The 12000 K source has a flux 256 times greater than a 3000 K source, so you'll need to adjust the vertical scale slider to fully see each curve. The colors under each curve indicates the perceived color of such a blackbody - blue at 12000 K, reddish-white at 6000K, and orangish-red at 3000 K.

Credit: The Nebraska Astronomy Applet Project, http://astro.unl.edu/naap/splash/.

http://astro.unl.edu/naap/ebs/spectraltype.html