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