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