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