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)(15,20)(16,27)(17,25)(18,23)(19,21)(22,24)(26,28) involution — undirected(5,7)(6,9)(8,12)(10,11)(13,14,18,23)(15,24,26,17)(16,21,19,27)(20,25,28,22)(2,4)(13,15,19,22,18,26,16,25)(14,20,21,24,23,28,27,17)(6,10)(9,11)(13,16,18,19)(14,21,23,27)(15,25,26,22)(17,20,24,28)(7,12)(9,11)(13,17,19,20,18,24,16,28)(14,22,21,26,23,25,27,15)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.