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