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