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