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