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