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