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)(13,14,18,17)(15,19,23,22)(16,20,26,25)(21,27,28,24)(5,7)(6,9)(8,12)(10,11)(13,15,18,23)(14,19,17,22)(16,24,26,27)(20,21,25,28)(2,4)(13,16,18,26)(14,20,17,25)(15,21,23,28)(19,27,22,24)(6,10)(9,11)(13,14,18,17)(15,19,23,22)(16,25,26,20)(21,24,28,27)(7,12)(9,11)(14,17)(15,22)(19,23)(20,25)(21,24)(27,28) involution — undirectedA 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.