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