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