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