Most often, colors are associated with binary stars. Binaries are stars that have formed in pairs, a common occurrence in nature, because human eyes are sensitive to contrast effects, subtle differences in the tints of these stars stand out when observed in a telescope. The colors in these stars arise from the fact that the outer layers of gas that form a star can be much different in temperature. Much like heating a piece of steel from a dull red to hotter orange and then white hot, stars display different colors depending upon their temperature. Therefore, cooler stars appear reddish or orange and the hotter stars seem white or blue-white.
Binary stars form a large part of our known universe.
One of the best things about observing double stars is that they can be easily seen from even light polluted areas. My backyard in the northeast corner of Ann Arbor is not by any stretch of the imagination a dark site. Separation is the apparent distance in arc seconds one star is from its companion. Well, that works most of the time, until you get two stars of equal brightness. Well, then you know you guessed wrong.