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