Alberio, a blue and yellow star. 

The double star Alberio marks the head of Cygnus, the Swan. It is high in the sky after midnight. You will need a telescope to see the two stars side by side, they are too close together to be seen easily with hand held binoculars.

Star colors are mostly a result of the temperature of the stars. Cool stars are red to orange, intermediate stars are yellow, and hot stars are white to blue-white in color. The fainter star in this pair is a sapphire blue, but it is much hotter than its brighter, topaz colored companion.