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