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