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