. . . Neurons are blue, and red, and green and some 87 other colors.  Neuroscientists at Harvard University have developed a methodology for using fluorescent proteins to color individual neurons within the brain.  Using a well-known recombinent system known as Cre/lox scientists have been able to build a transgene from portions of DNA, insert it into mouse DNA and cause the switching on of flourescent protein genes.  The technology allows researchers to see the individual neurons and connections of the brain in unparalled technicolor detail.

Link: ScienceDaily