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