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