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