Stars will form a variety of different spectral classes. The spectral class is a complicated word for the star's visible color. Colors range from blue to white to yellow to orange to red, starting at class 'O', deep blue, to class 'M', a deep red. If you have ever looked at a campfire, you would have noticed that the inner colors are white, and sometimes even bluish and as the fire moves outward, the colors become increasingly more yellow and red. A fire is hottern the center, so from this we can discern that the colors white and blue signify hotter fires than the colors yellow, orange, and red, which are actually a bit cooler. Strangely, this is the opposite of how we think of things, blue is usually thought of as a cool color and red and orange warm or hot. The same rule for heat and color applies to stars. The spectral type of a star also determines how long the star will last. Hotter stars burn more quickly, and therefore have a shorter lifespans. The opposite is true for cooler stars.