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