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