How do you know if a spirit is real?

In the picture given of Mr Murray's son, the hair is painted red—is it so in the spirit form?

It is so—his hair must have been red when in the body or it would not now appear so. There is no change in that which distinguishes the earth body. But when there has been a defect in the body, such as lameness, baldness, blindness, and such like, it is left with the body. In spirit life, you are complete in form and feature. 

The forms, features and colours of individual spirits may, and do vary, but all are perfect—defects have no place in the true spirit form. 

Take the case of an idiot in the earth life deprived of reason through some physical cause—no sooner does he emerge from the body than he is ushered into spirit life in his complete spiritual body with all the faculties of his nature in operation and much more acute, quicker in his apprehension of knowledge than others and this because he has not so much to unlearn—having learnt nothing in the ordinary way on earth—while others who have acquired a smattering of knowledge on earth and thereby become conceited get lazy or indifferent here, thinking they have got enough.

—Hafed, Prince of Persia