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