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