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