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