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