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