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