One vertex per element, one color per generator, with an edge from x to x·s.
(2,4)(5,6)(7,11)(8,9)(10,12)(14,17)(15,19)(22,26)(23,28) involution — undirected(6,8)(10,11)(13,14)(15,20)(16,17)(18,19)(21,22)(23,24)(25,26)(27,28) involution — undirected(7,12)(10,11)(14,17)(18,20)(21,23,25,28)(22,27,26,24)(1,2,3,4)(5,7,9,12)(6,10,8,11)(13,14)(15,20)(16,17)(18,19)(21,23)(22,27)(24,26)(25,28)(5,8,9,6)(7,10,12,11)(13,15,16,19)(14,18,17,20)(21,24,25,27)(22,28,26,23)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.