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