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