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