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