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