One vertex per element, one color per generator, with an edge from x to x·s.
(6,9)(7,11)(13,14)(15,20)(16,22)(17,23)(18,27)(19,24)(21,25)(26,28) involution — undirected(1,2)(3,4)(5,6,8,9)(7,10,11,12)(13,15,19,25)(14,20,24,21)(16,17,26,18)(22,23,28,27)(2,4)(13,16)(14,21)(15,18)(17,25)(19,26)(20,24)(22,27)(23,28) involution — undirected(5,7,8,11)(6,10,9,12)(13,16)(14,22)(15,17)(18,25)(19,26)(20,23)(21,27)(24,28)(2,4)(6,9)(10,12)(13,17,19,18)(14,23,24,27)(15,16,25,26)(20,22,21,28)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.