This function yields the node colors.
NodeColor(num.variable, num.situation, num.category, stage.structure,
range.color)
(numeric) - number of variables.
(vector) - number of stages associated with each variable.
(vector) - it identifies the number of edges that emanate from situations in each level.
list with two components:
numeric - score associated with a level
list of vectors - stage structure
(numeric) - it chooses the palette. If 1, it is used a 8-color palette. If 2, it is used a 501-color palette.
vector - node colors