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