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