presto-main/src/main/java/io/prestosql/util/GraphvizPrinter.java/GraphvizPrinter/visitValues
class GraphvizPrinter:        @Override
        public Void visitValues(ValuesNode node, Void context)
        {
            printNode(node, "Values", NODE_COLORS.get(NodeType.TABLESCAN));
            return null;
        }