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)(13,14,19,22,17,16,18,21)(15,23,27,24,25,20,26,28)(6,9)(10,12)(13,15)(14,20)(16,23)(17,25)(18,26)(19,27)(21,24)(22,28) involution — undirected(5,7)(6,10)(8,11)(9,12)(13,16,17,14)(15,24,25,28)(18,21,19,22)(20,27,23,26)(2,4)(7,11)(10,12)(14,16)(20,23)(21,22)(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.