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