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