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