This comet passed Earth in 2007, where I observed it from La Palma.
Like all color images it's composed from three different images with different color filters, as explained bottom of the previous page.
Usually the telescope follows the sky as the Earth rotates, but in this case it was set to follow the comet, which moves rather fast across the sky.
During the few minutes between each exposure, P/2007 moved moved a little, relative to the sky and the background stars.
Because of this, the stars are seen as three slightly shifted dots in different colors.