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