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)(15,22)(16,26)(17,21)(18,20)(19,25)(23,24)(27,28) involution — undirected(1,2)(3,4)(5,7,9,8)(6,10,12,11)(13,15)(14,19)(16,24)(17,25)(18,27)(20,23)(21,22)(26,28)(2,4)(13,14)(15,22)(16,26)(17,21)(18,20)(19,25)(23,24)(27,28) involution — undirected(2,4)(5,7,9,8)(6,11,12,10)(13,14)(15,23)(16,20)(17,21)(18,26)(19,27)(22,24)(25,28)(5,8,9,7)(6,11,12,10)(13,16,17,18)(14,20,21,26)(15,24,25,27)(19,23,22,28)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.