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