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