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