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