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