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