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