By looking at this site
it appears that the easiest way to tell an "Indigo Child" is by the poorly-applied soft focus effect on all of the photos of said child.
Although I will say that I have several photos of DS(3) where he has a whitish light around him and no one in the picture with him has the same light. And he does have a special connection with animals. We were at the seaside aquarium feeding the sealions and one of the newborn pups came over to Grayson and just sat there while they stared at each other. Until the pup mom barked at him to get back to her...lol It was so cool... He also has squirrels follow him through the park and sit by him on benches and such. But other than calling him our pet magnet that is about the only label tht he gets.
That all being said... I am not into the whole indigo child thing... He is an awesome kid and so are my other children they all have unique talents and gifts... So I think that it is a bunch of hooey and some of the traits listed we cause me to give the label of BRAT not something as lovely sounding as indigo.