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