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