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