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