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