This program simply takes two images, one taken in full colour and the other with an InfraRed passing filter such as the R25, R72 or R87.

The two images must have identical composition, and are separated into their RGB components. The Red layer from the IR image is then combined with the Red and Green of the Full colour image.

The light spectrum

Film has a different spectral sensitivity depending on the use the film is designed for. Some examples are shown in the diagram below.

The spectrum above shows the Ultraviolet, below 400nm,   400nm to 700nm is visible to the naked eye and above 700nm the near InfraRed light. 

You will also note the glass acts as a natural UV filter below 310nm.

You will need to check if you digital camera is capable of taking infrared shot by looking in its specifaction.  Many modern digital cameras have a built-in InfraRed blocking filter to improve the camera's noise immunity.