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