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