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