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