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