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)(15,22)(19,26)(23,25)(27,28) involution — undirected(1,2)(3,4)(6,10)(11,12)(15,23)(16,17)(19,27)(20,24)(22,25)(26,28) involution — undirected(2,4)(5,7,9,8)(6,11,10,12)(13,14,18,21)(15,19,22,26)(16,24,17,20)(23,27,25,28)(2,4)(13,15)(14,19)(16,23)(17,25)(18,22)(20,28)(21,26)(24,27) involution — undirected(5,8,9,7)(6,11,10,12)(13,16,18,17)(14,20,21,24)(15,23,22,25)(19,28,26,27)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.