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