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