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