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