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