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)(14,20)(17,21)(22,28)(24,26) involution — undirected(5,7,9,8)(6,10,12,11)(13,14)(15,24)(16,22)(17,27)(18,20)(19,28)(21,25)(23,26)(2,4)(5,7,9,8)(6,11,12,10)(13,15)(14,21)(16,25)(17,20)(18,23)(19,27)(22,26)(24,28)(5,8,9,7)(6,10,12,11)(13,16)(14,22)(15,23)(18,19)(20,28)(24,26)(13,17)(14,23)(15,20)(16,26)(18,21)(19,24)(22,25)(27,28) 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.