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