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