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