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