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