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