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