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