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