Раскраска графов жадным алгоритмом на SWI prolog

is_color_between_neighbours(GraphColors,Color,vertex(Number,NeighbourList)):-
    member(vertcol(Number,Color),NeighbourList).
try_colors_on_vertex(GraphColors,GraphColorsNew,Color,Vertex,Number):-
    ColorNew is Color + 1,
    is_color_between_neighbours(GraphColors,Color,Vertex) ->
        try_colors_on_vertex(GraphColors,GraphColorsNew,ColorNew,Vertex,Number)
        ;
        append([GraphColors,[vertcol(Number,ColorNew)]],GraphColorsNew).
 
get_vertex_by_number([],Number,Vertex,Counter):-!.
get_vertex_by_number([GraphHead|GraphTail],Number,Vertex,Counter):-
    CounterNew is Counter + 1,
    CounterNew =:= Number -> Vertex = GraphHead; get_vertex_by_number(GraphTail,Number,Vertex,CounterNew).
    
set_vertex_colors(Graph,GraphColors,Number):-
    NumberNew is Number + 1,
    Color is 0,
    Counter is 0,
    get_vertex_by_number(Graph,NumberNew,Vertex,Counter), %NumberNew - is actual number of considered on this iteration vertex.
    %try_colors_on_vertex(GraphColors,GraphColorsNew,Color,Vertex,NumberNew), %GraphColorsNew - support variable. It will contain concatenated list of colors
    set_vertex_colors(Graph,GraphColorsNew,NumberNew).
 
 
color_graph(A):-
    Graph = [vertex(1,[2]),vertex(2,[3]),vertex(3,[4]),vertex(4,[5]),vertex(5,[6]),vertex(6,[7]),vertex(7,[1])],
    GraphColors = [],
    Number = 0,
    set_vertex_colors(Graph,GraphColor,Number).
    %some print

get_vertex_by_number([],Number,Vertex,Counter):-!.