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