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