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