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