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