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