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