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