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