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