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