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