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