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