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