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