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