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