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