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