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