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