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)(13,14,18,22)(15,16,21,20)(17,23,26,27)(19,24,25,28)(5,7)(6,9)(8,12)(10,11)(13,15)(14,20)(16,22)(17,25)(18,21)(19,26)(23,24)(27,28) involution — undirected(1,2,3,4)(13,16,25,27,18,20,19,23)(14,21,28,17,22,15,24,26)(6,10)(9,11)(14,22)(16,20)(23,27)(24,28) involution — undirected(7,12)(9,11)(13,17,19,21,18,26,25,15)(14,23,24,20,22,27,28,16)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.