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