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