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