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