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