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