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