You can't. The information for that spectral band simply isn't there. Red captures around ~550 nm to ~700 nm. Near IR is > 700 nm wavelength. In fact camera manufacturers for most cameras put an infra red filter in front of the sensor, specifically to block (filter out) the infra red light.
If you have some special format where you somehow captured the NIR image and stored it along with the RGB images in a file, then you'll have to use an image reading function that can handle that format, such as the tiff class reader.
