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