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