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