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