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