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