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