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