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