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