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