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