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