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