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