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