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