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