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