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