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