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