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