We confess that we completely forgot Jeff Koons' birthday (it was January 21), but we're planning to make it up to him with the perfect belated gift: a femtosecond laser that can be used to change the color of virtually any metal he chooses! That's right--thanks to a newly discovered laser processing technique (again with the lasers!), Koons can zap up some gold aluminum, black gold, purple silver, and yes, blue steel.

The breakthrough, which was recently published in the journal Applied Physics Letters, is the work of University of Rochester optics professor Chunlei Guo and his assistant, Anatoliy Vorobeyv. How does it work? Well, in a nutshell, the ultra-fast, ultra-intense femtosecond (that's one billionth of one millionth of a second) laser restructures the surface of the metal, changing its optical properties and therefore, its color.

The metal-coloring research follows up on Guo's discovery of "black metal" in late 2006, when his team was able to create pitch black metal surfaces that absorbed virtually all light. "Now we finally can make a metal reflect almost any color we wish," says Guo. "When we first found the process that produced a gold color, we couldn't believe it. We worked in the lab until midnight trying to figure out what other colors we could make." In addition to creating metals that appear one color from all angles, Guo and Vorobyev have tweaked their technique to produce metals that exhibit different colors depending on one's point of view.