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