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