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