Create an XColor from an ArrayAtom of
containing PDF color values.
There may be only one, three or four items in the ArrayAtom. The
number of items is used to select between Grayscale, RGB or CMYK
color spaces respectively.
The values expected are PDF color values so all the atoms in the
ArrayAtom must be NumAtoms with a value between zero and one, each
representing a component of the color.
If these conditions are not met then an exception will be