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