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