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