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