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