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