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