One vertex per element, one color per generator, with an edge from x to x·s.
(5,6,8,7)(9,10)(11,19)(12,25)(13,16)(14,28)(15,22)(17,21)(18,26)(20,32)(23,33)(24,40)(27,29)(30,39)(31,36)(34,37)(35,38)(1,2)(3,4)(5,7,8,6)(9,11,20,36,14,24,12,22,13,23,21,37,26,38,27,39)(10,15,29,40,18,31,17,19,16,30,25,35,28,34,32,33)(2,4)(6,7)(10,16)(15,30)(17,32)(18,28)(19,33)(25,29)(31,34)(35,40) involution — undirected(9,11,21,37,14,24,27,39,13,23,20,36,26,38,12,22)(10,15,25,35,18,31,32,33,16,30,29,40,28,34,17,19)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.