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