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