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