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