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