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