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