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)(15,16)(17,19)(18,20)(21,22,25,23)(24,26,28,27)(6,9)(10,12)(13,15)(14,18)(16,19)(17,20)(22,23)(26,27) involution — undirected(7,11)(10,12)(14,19)(16,18)(21,22,25,23)(24,27,28,26)(1,2)(3,4)(5,6)(7,12)(8,9)(10,11)(13,15)(14,16)(17,20)(18,19)(21,23,25,22)(24,26,28,27)(5,7)(6,10)(8,11)(9,12)(13,16)(14,20)(15,19)(17,18)(21,24,25,28)(22,26,23,27)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.