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)(16,26)(17,23)(18,21)(19,22)(20,24)(27,28) involution — undirected(2,3)(5,6)(7,10)(8,9)(11,12)(13,15,19,18,20,26,17,27)(14,21,23,25,24,28,22,16)(1,2,4,3)(6,9)(10,11)(13,16,20,25)(14,15,24,26)(17,28,19,21)(18,22,27,23)(1,3,4,2)(5,7,8,12)(6,10,9,11)(13,17,20,19)(14,22,24,23)(15,18,26,27)(16,21,25,28)(13,18,17,15,20,27,19,26)(14,16,22,28,24,25,23,21)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.