Thermal imagery should be analyzed the same way as optical imagery (see Objects in gray scale images), as the images below show. Just like in regular gray scale images, there is only one parameter. Here, instead of the amount of light it is temperature.
The last image is "pseudo-color". Red means hot, blue means cool. In other words, red corresponds to higher values and blue to lower values of the parameter. A similar approach is used in mapping where the parameter is the altitude. There is still just one parameter.
It would, of course, be silly to analyze the fourth image as a color image.
Other image analysis examples