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)(15,21)(16,19)(17,20)(18,22)(23,26)(24,28)(25,27) involution — undirected(1,2)(3,4)(6,9)(10,11)(13,15,16,22)(14,18,19,21)(17,23,25,24)(20,28,27,26)(2,4)(15,22)(18,21)(23,24)(26,28) involution — undirected(2,4)(14,19)(15,23)(17,25)(18,26)(21,28)(22,24) involution — undirected(5,7,8,12)(6,10,9,11)(14,19)(18,21)(20,27)(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.