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