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