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