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