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