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