Long answer: Summary tasks are a collection of one or more child tasks. By definition, a summary task doesn’t represent any real work, resources, or deliverables, so summary tasks are neither on nor off the critical path of a project. Children of summary tasks can be on the critical path, assuming those children are not summary tasks themselves.
Nine. Well, so says Scott Berinato, in his book Good Charts. He bases this number on a conversation he had with Tamara Munzner, a data visualization expert and professor of computer science at the University of British Columbia. Here is an example Gantt chart with more than 8 colors.