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