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)(12,15)(13,18)(14,16)(19,24)(20,22)(21,23)(1,2)(3,6)(4,7)(5,8)(9,11,14,12)(10,15,16,17)(13,19,21,20)(18,22,23,24)(25,26,30,31)(27,29,33,38)(28,32,37,39)(34,36,35,40)(1,3,5,4)(2,6,8,7)(10,16)(15,17)(18,23)(22,24)(26,31)(29,38)(32,39)(36,40)(1,3,5,4)(2,6,8,7)(9,10)(11,15)(12,17)(13,18)(14,16)(19,22)(20,24)(21,23)(25,27,30,33)(26,29,31,38)(28,35,37,34)(32,40,39,36)(1,4,5,3)(2,7,8,6)(9,12,14,11)(10,17,16,15)(13,20,21,19)(18,24,23,22)(25,28)(26,32)(27,34)(29,36)(30,37)(31,39)(33,35)(38,40)(9,13,14,21)(10,18,16,23)(11,19,12,20)(15,22,17,24)(25,29)(26,33)(27,31)(28,36)(30,38)(32,35)(34,39)(37,40)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.