From the end of the plot synopsis:
During the closing credits, we see footage of the real Saroo introducing the real John and Sue Brierley to his birth mother in the Khandwa Village.
So, the change in the colour/tonality of the film at that point reinforces to the viewer that those scenes are external to the main plot.
The declared cameras used for this film are:
Obviously, the processing of the main film to obtain the tonality required would be digitally applied.
I don't see information on what camera was used for the end credit scenes, but you could assume that these are smaller, hand-held cameras - possibly DSLR cameras. The end scene is in effect a DVD Extra.