Hi Jeremy
In some ways you could say the sun is a medium size star - there are lots of stars larger than it (sometimes much larger) and lots smaller.
However, there are many more smaller stars than larger ones. Nine out of ten stars have less mass than the sun, so the sun is larger than most other stars.
The color of a star depends on its temperature. Red stars are relatively cool (for stars! - they still have surfaces at a few thousand degrees). Yellow and white ones are hotter and blue ones are even hotter.
Most stars spend much of their lives at a single color. These "middle aged" stars, like the sun, stay at the same size and color for a long time (about 10 billion years for the sun). At the end of this time they run out of fuel. This starts off a process in which the stars expand and cool to become red giant stars. Some very large stars (larger than the sun) even explode into supernovae during this time leaving behind a neutron star or even a black hole.
We don't expect the sun to do this, though. We expect that at the end of its red giant stage the sun will lose it outer atmosphere leaving behind a core called a white dwarf (another color change!), which will slowly fade.
None of this will happen for billions of years, though.
You can read more about the colors and lives of stars at the
Windows to the Universe web site here:
http://www.windows.ucar.edu/tour/link=/cool_stuff/tourstars_1.htmlTerry