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