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