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