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