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