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