Looking at your hair would not prove anything since people can dye their hair many colors, including brown, green, pink, purple, and etc. Observation is not always the only way to prove a truth.
Parapsychology has done a good job establishing the existence of unexplained phenomena, including pictures of "spirits". So there is affirmative evidence for the existence of a spirit world. Now, would you care to disprove this evidence?
Have you heard of "string theory"? Part of this theory is the existence of up to 11 dimensions. Since we as human beings can observe and experience only 4 dimensions you will have a hard time disproving scientifically what science is attempting to show is fact.