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