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