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