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