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