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