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