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