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