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