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)(15,25)(16,27)(17,22)(18,23)(19,24)(20,26)(21,28) involution — undirected(1,2,3,4)(7,8)(10,12)(13,15,17,26,19,27,18,21)(14,20,23,25,24,28,22,16)(5,7,9,8)(6,10,11,12)(13,16,18,28,19,25,17,20)(14,21,22,27,24,26,23,15)(5,8,9,7)(6,10,11,12)(13,14)(15,20)(16,21)(17,23)(18,22)(19,24)(25,26)(27,28)(13,17,19,18)(14,22,24,23)(15,26,27,21)(16,28,25,20)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.