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