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