Nope -- according to the family - dark brown. The pomade of course, which he wore up until his arrest, would make it appear even darker (pitch black) -
Without the pomade in prison, it would appear it's natural color of dark, dark brown. With it cut extremely short, it would probably appear lighter - maybe a medium brown with lighter highlights in the sun.
"The Past is a foreign country...they do things differently there" - L. P. Hartley