What is a trichrome?
A trichrome is a process in which three filtered black-and-white images are combined to create a full color image. While this is typically achieved with Red, Green, and Blue filters, color filters can be replaced with wavelengths beyond human vision.
Red can be replaced with Infrared, Green with Visible, and Blue with Ultraviolet. This is similar to the method used by space telescopes for full color images.