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